National Grid (NGG) 6-K 8 Nov 18 2019 Q2 Current report (foreign) Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Sep. 30, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	NATIONAL GRID PLC
Entity Central Index Key	1,004,315
Current Fiscal Year End Date	--03-31
Document Type	6-K
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,019
Document Fiscal Period Focus	Q2
Entity Current Reporting Status	Yes
Entity Accounting Standard	IFRS
Amendment Flag	false

Consolidated income statement

Consolidated income statement - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Statement1 [Line Items]
Revenue		£ 6,347	£ 6,684	[1]
Operating costs		(5,330)	(5,410)	[1]
Operating profit/(loss)		1,017	1,274	[1],[2]
Finance income		42	24	[1]
Finance costs		(562)	(538)	[1]
Share of post-tax results of joint ventures and associates		25	20	[1]
Profit/(loss) before tax		522	780	[1]
Tax		(93)	(153)	[1]
Profit/(loss) after tax from continuing operations		429	627	[1],[3]
Profit/(loss) after tax from discontinued operations		3	50	[1]
Total profit/(loss) for the period (continuing and discontinued)		432	677	[1]
Attributable To [Abstract]
Equity shareholders of the parent		431	676	[1]
Non-controlling interests	[4]	£ 1	£ 1	[1]
Earnings per share [abstract]
Basic earnings per share (continuing) (in GBP per share)		£ 0.127	£ 0.177	[1]
Diluted earnings per share (continuing) (in GBP per share)		0.126	0.176	[1]
Basic earnings per share (continuing and discontinued) (in GBP per share)		0.128	0.191	[1]
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ 0.127	£ 0.190	[1]
Before exceptional items and remeasurements [Member]
Statement1 [Line Items]
Revenue		£ 6,347	£ 6,684	[1]
Operating costs		(5,145)	(5,425)	[1]
Operating profit/(loss)		1,202	1,259	[1]
Finance income		42	24	[1]
Finance costs		(536)	(566)	[1]
Share of post-tax results of joint ventures and associates		25	20	[1]
Profit/(loss) before tax		733	737	[1]
Tax		(134)	(149)	[1]
Profit/(loss) after tax from continuing operations		599	588	[1]
Profit/(loss) after tax from discontinued operations		48	67	[1]
Total profit/(loss) for the period (continuing and discontinued)		647	655	[1]
Attributable To [Abstract]
Equity shareholders of the parent		646	654	[1]
Non-controlling interests	[4]	£ 1	£ 1	[1]
Earnings per share [abstract]
Basic earnings per share (continuing) (in GBP per share)		£ 0.178	£ 0.166
Diluted earnings per share (continuing) (in GBP per share)		0.177	0.165
Basic earnings per share (continuing and discontinued) (in GBP per share)		0.192	0.185
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ 0.191	£ 0.184
Exceptional items and remeasurements [Member]
Statement1 [Line Items]
Revenue		£ 0	£ 0	[1]
Operating costs		(185)	15	[1]
Operating profit/(loss)		(185)	15	[1]
Finance income		0	0	[1]
Finance costs		(26)	28	[1]
Share of post-tax results of joint ventures and associates		0	0	[1]
Profit/(loss) before tax		(211)	43	[1]
Tax		41	(4)	[1]
Profit/(loss) after tax from continuing operations		(170)	39	[1]
Profit/(loss) after tax from discontinued operations		(45)	(17)	[1]
Total profit/(loss) for the period (continuing and discontinued)		(215)	22	[1]
Attributable To [Abstract]
Equity shareholders of the parent		(215)	22	[1]
Non-controlling interests	[4]	£ 0	£ 0	[1]
Earnings per share [abstract]
Basic earnings per share (continuing) (in GBP per share)		£ (0.051)	£ 0.011
Diluted earnings per share (continuing) (in GBP per share)		(0.051)	0.011
Basic earnings per share (continuing and discontinued) (in GBP per share)		(0.064)	0.006
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ (0.064)	£ 0.006
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[3]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[4]	The non-controlling interests for the six month periods ended 30 September 2018 and 2017 relate to continuing operations.

Consolidated statement of compr

Consolidated statement of comprehensive income Statement - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Statement1 [Line Items]
Profit after tax from continuing operations		£ 429	£ 627	[1],[2]
Components of other comprehensive income that will not be reclassified to profit or loss, net of tax [abstract]
Remeasurement gains on pension assets and post-retirement benefit obligations		606	594	[2]
Net gains on investments in equity instruments designated at fair value through other comprehensive income		8	0	[2]
Net gains on financial liability designated at fair value through profit and loss attributable to changes in own credit risk		6	0	[2]
Net gains in respect of cash flow hedging of capital expenditure		13	0	[2]
Tax on items that will never be reclassified to profit or loss		(142)	(106)	[2]
Total items from continuing operations that will never be reclassified to profit or loss		491	488	[2]
Components of other comprehensive income that will be reclassified to profit or loss, net of tax [abstract]
Exchange adjustments		403	(262)	[2]
Net (losses)/gains in respect of cash flow hedges and cost of hedging		(31)	16	[2]
Transferred to profit or loss in respect of cash flow hedges and cost of hedging		27	6	[2]
Net gains on available-for-sale investments	[2]	0	10
Net gains on investments in debt instruments measured at fair value through other comprehensive income		8	0	[2]
Tax on items that may be reclassified subsequently to profit or loss		1	(3)	[2]
Total items from continuing operations that may be reclassified subsequently to profit or loss		408	(233)	[2]
Other comprehensive income for the period, net of tax, from continuing operations		899	255	[2]
Other comprehensive income for the period, net of tax, from discontinued operations2	[3]	36	64	[2]
Other comprehensive income for the period, net of tax		935	319	[2]
Total comprehensive income for the period from continuing operations		1,328	882	[2]
Total comprehensive income for the period from discontinued operations		39	114	[2]
Total comprehensive income for the period		1,367	996	[2]
Equity shareholders of the parent		1,365	996	[2]
Non-controlling interests	[4]	2	0	[2]
Quadgas Holdco Limited Cadent [Member]
Components of other comprehensive income that will be reclassified to profit or loss, net of tax [abstract]
Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans		35	60
Gains (losses) on cash flow hedges, net of tax		£ 1	£ 4
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[3]	The other comprehensive income from discontinued operations relates to items of other comprehensive income of Cadent (investment held through Quadgas Holdco Limited), comprising £35m (2017: £60m) remeasurement gains on pension assets and post-retirement benefit obligations, and £1m (2017: £4m) net gains in respect of cash flow hedges. Both items are shown net of tax.
[4]	The non-controlling interests for the six month periods ending 30 September 2018 and 30 September 2017 relate to continuing operations.

Consolidated statement of chang

Consolidated statement of changes in equity Statement - GBP (£) £ in Millions	Total		Issued capital [member]	Share premium [member]	Retained earnings [member]	Other Equity Reserves [Member]	Equity attributable to owners of parent [member]	Non-controlling interests [member]
Equity, beginning balance at Mar. 31, 2017	£ 20,384		£ 449	£ 1,324	£ 22,582	£ (3,987)	£ 20,368	£ 16
Profit for the period	677	[1]			676		676	1
Other comprehensive income for the period	319	[2]			548	(228)	320	(1)
Total comprehensive income for the period	996	[2]			1,224	(228)	996
Equity dividends	(4,141)				(4,141)		(4,141)
Scrip dividend related share issue			1	(1)
Issue of treasury shares	28				28		28
Purchase of treasury shares	(413)				(413)		(413)
Purchase of own shares	(5)				(5)		(5)
Share-based payment	23				23		23
Equity, ending balance at Sep. 30, 2017	16,872		450	1,323	19,298	(4,215)	16,856	16
Equity, beginning balance at Mar. 31, 2018	18,848
Equity, beginning balance (Increase (decrease) due to changes in accounting policy required by IFRS 9 and IFRS 15 [Member]) at Mar. 31, 2018	(196)				(268)	72	(196)
Equity, beginning balance (Previously stated [member]) at Mar. 31, 2018	18,848		452	1,321	21,599	(4,540)	18,832	16
Equity, beginning balance (Currently stated [member]) at Mar. 31, 2018	18,652		452	1,321	21,331	(4,468)	18,636	16
Profit for the period	432				431		431	1
Other comprehensive income for the period	935				505	429	934	1
Total comprehensive income for the period	1,367				936	429	1,365	2
Equity dividends	(710)				(710)		(710)
Scrip dividend related share issue			5	(5)
Issue of treasury shares	16				16		16
Purchase of own shares	(2)				(2)		(2)
Share-based payment	16				16		16
Cash flow hedges transferred to the statement of financial position, net of tax	(4)					(4)	(4)
Equity, ending balance at Sep. 30, 2018	£ 19,335		£ 457	£ 1,316	£ 21,587	£ (4,043)	£ 19,317	£ 18
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Consolidated statement of finan

Consolidated statement of financial position - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Non-current assets
Goodwill	£ 5,860	£ 5,444
Other intangible assets	990	899
Property, plant and equipment	42,661	39,853
Other non-current assets	96	115
Pension assets	1,754	1,409
Financial and other investments	613	899
Investments in joint ventures and associates	670	2,168
Derivative financial assets	1,159	1,319
Total non-current assets	53,803	52,106
Current assets
Inventories and current intangible assets	440	341
Trade and other receivables	2,335	2,798
Current tax assets	89	114
Financial and other investments	1,658	2,694	£ 2,573	£ 8,741
Derivative financial assets	189	405
Cash and cash equivalents	130	329	39	1,139
Assets held for sale	2,121	0
Total current assets	6,962	6,681
Total assets	60,765	58,787
Current liabilities
Borrowings	(4,134)	(4,447)
Derivative financial liabilities	(355)	(401)
Trade and other payables	(3,144)	(3,453)
Contract liabilities	(26)	0
Current tax liabilities	(137)	(123)
Provisions	(379)	(273)
Liabilities held for sale	(50)	0
Total current liabilities	8,225	8,697
Non-current liabilities
Borrowings	(23,510)	(22,178)
Derivative financial liabilities	(780)	(660)
Other non-current liabilities	(868)	(1,317)
Contract liabilities	(834)	0
Deferred tax liabilities	(3,902)	(3,636)
Pensions and other post-retirement benefit obligations	(1,424)	(1,672)
Provisions	(1,887)	(1,779)
Total non-current liabilities	33,205	31,242
Total liabilities	41,430	39,939
Net assets	19,335	18,848
Equity
Share capital	457	452
Share premium account	1,316	1,321
Retained earnings	21,587	21,599
Other equity reserves	(4,043)	(4,540)
Total shareholders’ equity	19,317	18,832
Non-controlling interests	18	16
Total equity	£ 19,335	£ 18,848	£ 16,872	£ 20,384

Consolidated cash flow statemen

Consolidated cash flow statement - GBP (£) £ in Millions		6 Months Ended			12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017		Mar. 31, 2018
Adjustments to reconcile profit (loss) [abstract]
Operating profit from continuing operations		£ 1,017	£ 1,274	[1],[2]
Exceptional items and remeasurements		185	(15)	[2]
Depreciation and amortisation		791	762	[2]
Share-based payment charge		16	23	[2]
Changes in working capital		190	153	[2]
Changes in provisions		(10)	(51)	[2]
Changes in pensions and other post-retirement benefit obligations		(128)	(124)	[2]
Cash flows relating to exceptional items		(120)	0	[2]
Cash generated from continuing operations		1,941	2,022	[2]
Tax (paid)/received		(6)	46	[2]
Net cash flow from operating activities – continuing operations		1,935	2,068	[2]
Net cash flow (used in)/from operating activities – discontinued operations	[2],[3]	(47)	(126)
Cash flows from investing activities [abstract]
Acquisition of investments3	[4]	(19)	(1)	[2]
Investments in joint ventures and associates		(84)	(77)	[2]
Loans to joint ventures and associates		(11)	(38)	[2]
Purchases of intangible assets		(140)	(73)	[2]
Purchases of property, plant and equipment		(1,765)	(1,768)	[2]
Disposals of property, plant and equipment		10	2	[2]
Dividends received from joint ventures and associates		33	29	[2]
Interest received		31	20	[2]
Net movements in short-term financial investments		1,157	6,130	[2]
Net cash flow (used in)/from investing activities – continuing operations		(788)	4,224	[2]
Cash flows from (used in) investing activities, discontinued operations	[5]	78	15	[2]
Cash flows from financing activities [abstract]
Purchase of own shares		(2)	(5)	[2]
Proceeds from issue of treasury shares		16	28	[2]
Purchase of treasury shares		0	(413)	[2]
Proceeds received from loans		1,116	1,091	[2]
Repayments of loans		(1,575)	(1,471)	[2]
Net movements in short-term borrowings and derivatives		208	(1,717)	[2]
Interest paid		(433)	(421)	[2]
Dividends paid to shareholders		(710)	(4,141)	[2]
Net cash flow used in financing activities – continuing operations		(1,380)	(7,049)	[2]
Net cash flow (used in)/from financing activities – discontinued operations	[3],[6]	0	(231)	[2]
Net decrease in cash and cash equivalents		(202)	(1,099)	[2]
Exchange movements		3	(1)	[2]
Net cash and cash equivalents at start of period		329	1,139	[2]	£ 1,139	[2]
Net cash and cash equivalents at end of period		£ 130	£ 39	[2]	£ 329
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[3]	Cash flows used in discontinued operating activities in both 2018 and 2017 related to the disposal of the UK Gas Distribution business.
[4]	Acquisition of investments includes Technology and Innovation investments.
[5]	Cash flows from discontinued investing activities relates to the receipt of £66m (2017: £nil) of dividends and £12m (2017: £15m) of interest on the shareholder loan from our investment in Quadgas HoldCo Limited (see note 6).
[6]	Cash flows used in discontinued financing activities in 2017 related to the liability management programme related to the UK Gas Distribution business.

Consolidated cash flow statem_2

Consolidated cash flow statement - Footnotes - Discontinued operations [member] - Quadgas HoldCo Limited [Member] - GBP (£)	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement1 [Line Items]
Dividends received	£ 66,000,000	£ 0
Interest income on loans and receivables	£ 12,000,000	£ 15,000,000

Basis of preparation and new ac

Basis of preparation and new accounting standards, interpretations and amendments	6 Months Ended
	Sep. 30, 2018
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Basis of preparation and new accounting standards, interpretations and amendments	Basis of preparation and new accounting standards, interpretations and amendments The half year financial information covers the six month period ended 30 September 2018 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB) and as adopted by the European Union (EU); and the Disclosure and Transparency Rules of the Financial Conduct Authority. This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2018 and 2017 , together with the audited consolidated statement of financial position at 31 March 2018 . The financial information for the year ended 31 March 2018 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2018 , which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB and as adopted by the EU, and have been filed with the Registrar of Companies. The Deloitte LLP audit report on these statutory accounts was unqualified, did not contain an emphasis of matter and did not contain a statement under Section 498 of the Companies Act 2006. The half year financial information has been prepared in accordance with the accounting policies expected to be applicable for the year ending 31 March 2019 . The notes to the financial statements have been prepared on a continuing basis unless otherwise stated. The Group has adopted IFRS 9 'Financial Instruments' and IFRS 15 'Revenue from Contracts with Customers' for the first time with effect from 1 April 2018. Other than in this respect, the half year financial statements have been prepared on a basis consistent with that applied in the preparation of the financial statements for the year ended 31 March 2018 , other than as outlined below in relation to discontinued operations. Our consolidated income statement and segmental analysis (see note 2) separately identify financial results before and after exceptional items and remeasurements. The Directors believe that presentation of the results in this way is relevant to an understanding of the Group’s financial performance. Presenting financial results before exceptional items and remeasurements is consistent with the way that financial performance is measured by management and reported to the Board and Executive Committee and improves the comparability of reported financial performance from year to year. Events or transactions which are classified as exceptional items or remeasurements are defined in the Annual Report and Accounts and Form 20-F. We continue to adopt a columnar presentation as we consider it improves the clarity of the presentation, and is consistent with the way that financial performance is measured by management and reported to the Board and Executive Committee, and better enables users of the financial statements to understand the results. The inclusion of total profit for the period from continuing operations before exceptional items and remeasurements forms part of the incentive target set annually for remunerating certain Executive Directors and accordingly we believe it is important for users of the financial statements to understand how this compares to our results on a statutory basis and period on period. Areas of judgement and key sources of estimation uncertainty In preparing this half year financial information, the areas where judgement has been exercised by management in applying the Group’s accounting policies and the key sources of estimation uncertainty remain consistent with those applied to the Annual Report and Accounts for the year ended 31 March 2018 . In applying the Group’s exceptional items framework for the half year, we have considered three key matters. As described further in note 4, we have concluded that the costs associated with the Massachusetts Gas work continuation ( £97m ) and the UK cost efficiency and restructuring programme ( £127m ) should be treated as exceptional. We also considered whether the £94m income from two legal settlements received in the period should also be classified as exceptional. However, we concluded it was appropriate to recognise the income in earnings before exceptional items (within Other Activities), in line with the treatment of the original costs. In addition, in preparing the half year financial information, we have exercised our judgement in concluding that it is appropriate to classify our investment in and shareholder loan to Quadgas HoldCo Limited (Quadgas), along with the related Further Acquisition Agreement (FAA) and Remaining Acquisition Agreement (RAA) derivatives, as held for sale and as a discontinued operation, as detailed in note 6. 1. Basis of preparation and new accounting standards, interpretations and amendments (continued) Going concern Having made enquiries and reassessed the principal risks, the Directors consider that the Company and its subsidiary undertakings have adequate resources to continue in business for the foreseeable future, being a period of not less than 12 months from the date of this report. Accordingly, it is appropriate to adopt the going concern basis in preparing the half year financial information. New IFRS accounting standards and interpretations adopted in the period The Group has adopted IFRS 9 ‘Financial Instruments’ and IFRS 15 ‘Revenue from Contracts with Customers’ for the first time with effect from 1 April 2018. Refer to note 17 for details of the impact and transition adjustments arising on adoption. There are no other new standards, interpretations and amendments, issued by the IASB or by the IFRS Interpretations Committee (IFRIC), that are applicable for the period commencing on 1 April 2018 that have had a material impact on the Group’s results. New IFRS accounting standards and interpretations not yet adopted The Group continues to assess the impact of IFRS 16 'Leases', which will be implemented on 1 April 2019. The Group enters into a significant number of operating lease transactions. Under IFRS 16, our operating leases will be accounted for on the consolidated statement of financial position as ‘right-of-use’ assets. This treatment will increase both our assets and liabilities and subsequently, will result in an increase in finance costs and depreciation and a reduction in operating costs. We continue to assess our revenue, service contracts and power purchase contracts to determine whether we have the right to use assets under those contracts and whether they fall within the scope of IFRS 16. We plan to apply IFRS 16 using the modified retrospective approach, whereby comparatives will not be restated on adoption of the new standard but instead a cumulative adjustment will be reflected in retained earnings. We will provide further details of the impact that the implementation of IFRS 16 will have in the Annual Report and Accounts for the year ending 31 March 2019. There are no new accounting standards and amendments to existing standards that have been issued, but are not yet effective or have not yet been endorsed by the EU that were not disclosed in our Annual Report and Accounts. The Group has not early adopted any standard, amendment or interpretation that has been issued but is not yet effective.

Segmental analysis

Segmental analysis	6 Months Ended
	Sep. 30, 2018
Operating Segments [Abstract]
Segmental analysis	Segmental analysis We present revenue and the results of the business analysed by operating segment, based on the information the Board of Directors uses internally for the purposes of evaluating the performance of operating segments and determining resource allocation between operating segments. The Board is National Grid’s chief operating decision-making body (as defined by IFRS 8 ‘Operating Segments’) and assesses the profitability of operations principally on the basis of operating profit before exceptional items and remeasurements (see note 4). As a matter of course, the Board also considers profitability by segment, excluding the effect of timing. The following table describes the main activities for each reportable operating segment: UK Electricity Transmission The high voltage electricity transmission network in England and Wales and Great Britain system operator. UK Gas Transmission The high pressure gas transmission network and system operator in Great Britain. US Regulated Gas distribution networks, electricity distribution networks and high voltage electricity transmission networks in New York and New England and electricity generation facilities in New York. National Grid Ventures (NGV) does not meet the thresholds set out in IFRS 8 to be identified as a separate reportable segment and therefore its results have not been disaggregated. Other activities that do not form part of any of the segments in the above table primarily relate to UK property development together with insurance and corporate activities in the UK and US and the Group’s investments in Technology and Innovation companies. Sales between operating segments are priced having regard to the regulatory and legal requirements to which the businesses are subject. The analysis of revenue by geographical area is on the basis of destination. There are no material sales between the UK and US geographical areas. The US Regulated segment typically experiences seasonal fluctuations in revenue and operating profit due to higher delivery volumes during the second half of the financial year, for example as a result of extreme weather over the winter. These seasonal fluctuations have a consequential impact on the working capital balances (primarily trade debtors and accrued income) in the consolidated statement of financial position at 30 September 2018 when compared to 31 March 2018 . The majority of UK revenues are governed by the arrangements under RIIO, through which revenue is primarily based on availability of transmission capacity rather than usage, and therefore are not subject to the same seasonal fluctuations as in the US. (a) Revenue Six months ended 30 September 2018 2017 £m £m Operating segments - continuing operations: UK Electricity Transmission 1,574 2,076 UK Gas Transmission 353 422 US Regulated 4,053 3,799 NGV and Other 1 387 407 Sales between segments (20 ) (20 ) Total revenue from continuing operations 6,347 6,684 Geographical areas: UK 2,272 2,865 US 4,075 3,819 Total revenue from continuing operations 6,347 6,684 1. Included within NGV and Other is £294m ( 2017 : £294m ) of revenue relating to NGV and £44m (2017: £59m ) of revenue relating to UK property development. 2. Segmental analysis (continued) (b) Operating profit Before exceptional items and remeasurements 1 After exceptional items and remeasurements 1 Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 531 542 437 542 UK Gas Transmission 79 126 46 126 US Regulated 385 433 327 448 NGV and Other 2, 3 207 158 207 158 Total operating profit from continuing operations 1,202 1,259 1,017 1,274 Geographical areas UK 761 852 634 852 US 441 407 383 422 Total operating profit from continuing operations 1,202 1,259 1,017 1,274 Below we reconcile total operating profit to profit before tax from continuing operations. Operating exceptional items and remeasurements of £94m expense (2017: £ nil ) detailed in note 4 are attributable to UK Electricity Transmission; £33m expense (2017: £ nil ) to UK Gas Transmission; and £58m expense ( 2017 : £15m income) to US Regulated operations. Before exceptional items and remeasurements 1 After exceptional items and remeasurements 1 Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m Reconciliation to profit before tax: Operating profit - continuing operations 1,202 1,259 1,017 1,274 Share of post-tax results of joint ventures and associates 25 20 25 20 Finance income 42 24 42 24 Finance costs (536 ) (566 ) (562 ) (538 ) Profit before tax from continuing operations 733 737 522 780 1. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6). 2. Included within NGV and Other is £ 131 m ( 2017 : £132m ) of operating profit (both before and after exceptional items and remeasurements) relating to NGV and £38m (2017: £53m ) of operating profit (both before and after exceptional items and remeasurements) relating to UK property development. 3. NGV and Other includes gains of £94m (2017: £ nil ) in relation to cash received in respect of two legal settlements. 2. Segmental analysis (continued) (c) Other segmental information Net book value 1 Capital expenditure 2 Depreciation and amortisation 3 30 September 2018 31 March 30 September 2018 30 September 2017 30 September 2018 30 September 2017 £m £m £m £m £m £m Operating segments: UK Electricity Transmission 13,247 13,028 462 515 (242 ) (226 ) UK Gas Transmission 4,345 4,280 153 157 (92 ) (94 ) US Regulated 23,395 20,953 1,177 1,095 (346 ) (328 ) NGV and Other 4, 5 2,664 2,491 248 125 (111 ) (114 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) Geographical areas: UK 19,094 18,772 782 751 (399 ) (393 ) US 24,557 21,980 1,258 1,141 (392 ) (369 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) By asset type: Property, plant and equipment 42,661 39,853 1,900 1,820 (710 ) (689 ) Non-current intangible assets 990 899 140 72 (81 ) (73 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) 1. Represents the net book value of property, plant and equipment and other non-current intangible assets at 30 September 2018 and 31 March 2018 respectively. 2. Represents additions to property, plant and equipment and other non-current intangibles, in the six months ended 30 September 2018 and 30 September 2017 respectively. 3. Represents the amounts recorded in the consolidated income statement for the six months ended 30 September 2018 and 30 September 2017 respectively. 4. Included within NGV and Other are assets with a net book value of £1,518m and £60m ( 31 March 2018 : £1,454m and £52m ), capital expenditures of £136 m and £11m ( 2017 : £72m and £5m ) and depreciation and amortisation of £64 m and £1m ( 2017 : £68m and £ nil ) relating to NGV and UK property development respectively. 5. Net book value for NGV and Other includes certain software assets and properties in the US which are outside the US rate base and operate for the benefit of our US regulated businesses. Costs associated with owning and operating these assets (principally depreciation and amortisation) are recharged to the US regulated business.

Revenue

Revenue	6 Months Ended
	Sep. 30, 2018
Revenue from Contracts with Customers [Abstract]
Revenue	Revenue IFRS 15 ‘Revenue from Contracts with Customers’ is effective for periods from 1 April 2018. As explained further in note 17, the standard has been applied prospectively and therefore the analysis below is only provided for the current period. The impact of adoption on the opening balance sheet and reserves is not material, with the main change being in relation to customer connection income. Under IFRS 15, revenue is recorded as or when the Group satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is transferred when the customer obtains control of that good or service. The transfer of control of our distribution or transmission services coincides with the use of our network, as electricity and gas pass through our network and reach our customers. The Group principally satisfies its performance obligations over time and the amount of revenue recorded corresponds to the amounts billed and accrued for volumes of gas and electricity delivered/transferred to/from our customers. The revenue recognition policies for the non-regulated businesses are not impacted by the adoption of IFRS 15. Note 17 includes the quantification of the impact for the half year if revenue were still to have been accounted for under IAS 18. Revenue for the six months ended 30 September 2018 UK Electricity Transmission £m UK Gas Transmission £m US Regulated £m NG Ventures and Other £m Total £m Revenue under IFRS 15 Transmission 1,559 322 315 152 2,348 Distribution — — 3,478 — 3,478 Other 1 — — — 138 138 Total IFRS 15 revenue 1,559 322 3,793 290 5,964 Other revenue 2 Generation — — 183 — 183 Other 3 25 77 95 200 Total other revenue 3 25 260 95 383 Total revenue from continuing operations 1,562 347 4,053 385 6,347 Geographic split of revenue for the six months ended 30 September 2018 UK Electricity Transmission £m UK Gas Transmission £m US Regulated £m NG Ventures and Other £m Total £m Revenue under IFRS 15 UK 1,559 322 — 290 2,171 US — — 3,793 — 3,793 Total IFRS 15 revenue 1,559 322 3,793 290 5,964 Other revenue UK 3 25 — 73 101 US 2 — — 260 22 282 Total other revenue 3 25 260 95 383 Total revenue from continuing operations 1,562 347 4,053 385 6,347 1. Other IFRS 15 revenue relates to revenue generated from metering businesses. 2. Other revenue principally consists of income relating to US generation contracts where we act as lessor under the leasing standard (IAS 17).

Exceptional items and remeasure

Exceptional items and remeasurements	6 Months Ended
	Sep. 30, 2018
Exceptional Items And Remeasurements [Abstract]
Exceptional items and remeasurements	Exceptional items and remeasurements Exceptional items and remeasurements are items of income and expenditure that, in the judgement of the Directors, should be disclosed separately on the basis that they are important to an understanding of our financial performance and significantly distort the comparability of financial performance between periods. Remeasurements comprise gains or losses recorded in the consolidated income statement arising from changes in the fair value of certain financial assets and liabilities categorised as held at fair value through profit and loss. These include financial assets that fail the solely payments of principal and interest test, financial liabilities designated at fair value through profit and loss excluding gains and losses attributable to changes in the Company’s own credit risk, commodity contracts and derivative financial instruments used in our financing activities to the extent that hedge accounting is either not achieved or is not effective. Six months ended 30 September 2018 Exceptional items Remeasurements Total £m £m £m Included within operating profit from continuing operations UK cost efficiency and restructuring programme 1 (127 ) — (127 ) Massachusetts Gas work continuation 2 (97 ) (97 ) Net gains on commodity contract derivatives 3(i) — 39 39 (224 ) 39 (185 ) Included within net finance costs (note 5) Net losses on derivative financial instruments 3(ii) — (26 ) (26 ) Net gains on FVTPL financial assets 3(iii) — 8 8 Net losses on FVTPL financial liabilities 3(iv) — (8 ) (8 ) — (26 ) (26 ) Total included within profit before tax from continuing operations (224 ) 13 (211 ) Tax 48 (7 ) 41 Total exceptional items and remeasurements after tax from continuing operations (176 ) 6 (170 ) Six months ended 30 September 2017 Exceptional items 4 Remeasurements 4 Total 4 £m £m £m Included within operating profit from continuing operations Net gains on commodity contract derivatives 3(i) — 15 15 — 15 15 Included within net finance costs (note 5) Net gains on derivative financial instruments 3(ii) — 28 28 28 28 Total included within profit before tax from continuing operations — 43 43 Tax — (4 ) (4 ) Total exceptional items and remeasurements after tax from continuing operations — 39 39 1. UK cost efficiency and restructuring programme: In July 2018, our UK business consulted on a series of significant restructuring activities relating to our core UK regulated activities in anticipation of the upcoming RIIO-T2 price control. During the period we completed a comprehensive review of the organisational structure, certain operational activities, and relevant roles and responsibilities across Electricity Transmission and Gas Transmission, with changes communicated ahead of 30 September. By 30 September 2018 we had provided over £100m associated with severance costs, with the remainder of the £127m exceptional charge relating to associated support and planning costs. We expect some further costs will be incurred during the second half of the year as we complete our transition. On the basis that this item is material for the half year results and the full year financial statements, we have treated the costs as exceptional. The cash outflow for the period was £18m . 4. Exceptional items and remeasurements (continued) 2. Massachusetts Gas work continuation: On 25 June 2018, National Grid implemented a workforce contingency plan across its Massachusetts Gas business following the expiration of contracts for the existing workforce. Since then we have employed experienced contractors alongside supervisors and workers from other areas of our business to ensure work continues safely. In view of the significance of this item to the half year results and on the basis that it will be material to the full year financial statements, we have treated the incremental direct and associated incidental costs as exceptional. As at 30 September 2018, the incremental costs totalled $127m ( £97m ). The total cash outflow related to the work continuation for the period was $134m ( £102m ). 3. Remeasurements on derivative financial instruments: i. Net gains/(losses) on commodity contract derivatives represent mark-to-market movements on certain physical and financial commodity contract obligations in the US. These contracts primarily relate to the forward purchase of energy for supply to customers, or to the economic hedging thereof, that are required to be measured at fair value and do not qualify for hedge accounting. Under the existing rate plans in the US, commodity costs are recoverable from customers although the timing of recovery may differ from the pattern of costs incurred. ii. Net gains/(losses) on derivative financial instruments comprise gains/(losses) arising on derivative financial instruments reported in the consolidated income statement in relation to our debt financing and foreign exchange hedging of the investment funds held by our insurance captives. These exclude gains and losses for which hedge accounting has been effective, and have been recognised directly in other comprehensive income or are offset by adjustments to the carrying value of debt. iii. Net gains/(losses) on fair value through profit and loss (FVTPL) financial assets comprise gains/(losses) on the investment funds held by our insurance captives and Group money market fund investments which are categorised as fair value through profit and loss (see note 17). iv. Net gains/(losses) on FVTPL financial liabilities comprises the change in the fair value (excluding changes due to own credit risk) of a financial liability that has been designated at fair value through profit and loss on transition to IFRS 9 to reduce a measurement mismatch (see note 17). 4. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Finance income and costs

Finance income and costs	6 Months Ended
	Sep. 30, 2018
Analysis of income and expense [abstract]
Finance income and costs	Finance income and costs Six months ended 30 September 2018 2017 Notes £m £m Finance income before exceptional items and remeasurements Interest income on financial instruments 1 42 24 42 24 Finance costs before exceptional items and remeasurements Net interest payable on pensions and other post-retirement benefit obligations (11 ) (33 ) Interest expense on financial instruments (555 ) (546 ) Unwinding of discount on provisions (35 ) (38 ) Other interest (9 ) (8 ) Less: Interest capitalised 74 59 (536 ) (566 ) Net finance costs before exceptional items and remeasurements (494 ) (542 ) Total exceptional items and remeasurements 4 (26 ) 28 Net finance costs including exceptional items and remeasurements from continuing operations (520 ) (514 ) 1. Comparatives have been re-presented to reflect the classification of £15m of interest income in respect of our loan to Quadgas as a discontinued operation in the current period (see note 6).

Held for sale and discontinued

Held for sale and discontinued operations – Interests in Quadgas HoldCo Limited	6 Months Ended
	Sep. 30, 2018
Non-current Assets Held For Sale And Discontinued Operations [Abstract]
Held for sale and discontinued operations – Interests in Quadgas HoldCo Limited	Held for sale and discontinued operations – Interests in Quadgas HoldCo Limited On 31 March 2017, the Group sold 61% of its UK Gas Distribution business to Quadgas BidCo Limited (the Consortium) and retained 39% of the business. At the same time, we and the Consortium also entered into a Further Acquisition Agreement (FAA) in a put/call arrangement to sell a further 14% of our investment in the business between 1 March 2019 and 30 June 2019 (our put, having given at least six months’ notice) or between 1 July 2019 to 31 October 2019 (the Consortium’s call, having given six months’ notice). On 1 May 2018, we announced that we had entered into a Remaining Acquisition Agreement (RAA) with the Consortium for the remaining 25% stake in the business under an agreement similar to the FAA. The pricing under the RAA is less favourable to the Group, however, in all other material aspects, the RAA is similar to the FAA, in particular as regards the windows for the notice to be given and exercise of the put and call options. In our 2018 financial statements, the aggregate carrying value of our investment in Quadgas at 31 March 2018 was £2.1 bn, determined with reference to the future proceeds expected to be received under the FAA and RAA. We have decided to exercise the options over our remaining 39% interest in Cadent and the sale is expected to complete at the end of June 2019, subject to customary regulatory approvals. Assets and liabilities held for sale Under IFRS, the reclassification of assets (and any associated liabilities) as 'held for sale' can only be triggered once the assets are available for sale in their present condition and the sale is 'highly probable'. The highly probable criteria is met when the sale is expected to be completed within a year. We have therefore classified our interests in Quadgas as 'held for sale' with effect from 30 June 2018, since we expect to exit our investment on 30 June 2019. At 31 March 2018, we had no such expectation of sale completion within a year. The aggregate carrying value of the assets and liabilities we will exit was £2.1 bn at 30 September 2018, reflecting the total proceeds that remain to be received. No discounting has been applied on the basis that the period to exercise is now less than a year. The value allocated to each element of the Quadgas disposal group at 30 September 2018 is as follows: • the shareholder loan receivable is valued at par of £0.4 bn; • the RAA derivative liability 1 is valued at £43m , being £ nil less any cash proceeds relating to the RAA received to date; • the FAA derivative asset 1 is valued at £87 m and has been determined by comparing the pricing mechanism within the FAA against that in the RAA less cash proceeds relating to the FAA received to date; and • the residual balance of £1.6 bn has been allocated to the investment in associate. Treatment as a discontinued operation We consider that the exercise of our put options is the final stage of the plan to dispose of our interest in the UK Gas Distribution business first announced in 2015, and have accordingly treated the results and cash flows arising from Quadgas as a discontinued operation in the current period on the basis that the sale forms part of 'a single coordinated plan' to dispose of UK Gas Distribution. As a consequence, we have classified the various elements of income, expense and cash flows within discontinued operations as set out below, with comparatives also re-presented accordingly: Consolidated income statement - discontinued operations: • £38m of income arising from our post-tax share of the profits of Quadgas Holdco Limited for the three months to 30 June 2018 2 (2017: £52m ); • £12 m of shareholder loan interest receivable (and tax thereon) for the six months to 30 September 2018; (2017: £15 m); • Impairment charge of £43m (treated as a non-deductible expense for tax purposes), largely offsetting the gains recognised through other comprehensive income in relation to Quadgas' defined benefit pensions arrangement, and £2m of other costs for the three months to 30 June 2018 (2017: £ nil ); and • Tax charge of £2m (2017: £3m ). 6. Held for sale and discontinued operations – Interests in Quadgas HoldCo Limited (continued) Consolidated cash flow statement - discontinued operations: • £66m of dividends received in the period (2017: £ nil ); and • £12m of interest received on the shareholder loan (2017: £15m ). Consolidated statement of other comprehensive income - discontinued operations: • A gain of £35m relating to pensions, net of deferred tax, for the three month period to 30 June 2018 2 (2017: £60m ); and • £1m of gains in respect of cash flow hedges for the three month period to 30 June 2018 2 (2017: £4m ). 1. The RAA and FAA are both level 3 financial instruments. No sensitivity analysis is provided in respect of the FAA and RAA derivatives. The price at which we will exit our interest in Quadgas HoldCo Limited is fixed, and accordingly reflected in the aggregate carrying value of the disposal group. Any change in the fair value of these derivatives at 30 September would have been offset by equal and opposite adjustments to the carrying value of our equity interest, with nil net impact on profit and loss for the period. 2. Once the assets are treated as ‘held for sale’ equity accounting ceases for our investment in our associate. We therefore ceased to record our share of profits and share of gains/losses recorded within other comprehensive income from this date.

Tax from continuing operations

Tax from continuing operations	6 Months Ended
	Sep. 30, 2018
Income Taxes [Abstract]
Tax from continuing operations	Tax from continuing operations The tax charge for the six month period is £93m ( 2017 re-presented: £153m ), and excluding tax on exceptional items and remeasurements, is £134m ( 2017 re-presented: £149m ). The effective tax rate excluding tax on exceptional items and remeasurements is 18.3% (2017 re-presented: 20.2% ), which includes our share of post-tax results of joint ventures and associates and is based on the best estimate of the weighted average annual income tax rate by jurisdiction expected for the full year. The current period rate reflects the seasonality of earnings in the US. For the full year, we expect the Group effective tax rate to be around 20% excluding tax on exceptional items and remeasurements. This includes the effect of the reduction in the US corporate tax rate resulting from the Tax Cuts and Jobs Act (Tax Reform). The effective tax rate for the year ended 31 March 2018 (re-presented) was (33.4)% , and 23.4% before exceptional items and remeasurements. Further details on Tax Reform are provided on page 119 of the Annual Report and Accounts. The Finance Act 2016 which was enacted on 15 September 2016, reduced the main rate of corporation tax in the UK to 17% with effect from 1 April 2020. UK deferred tax balances have been calculated at this rate.

Earnings per share

Earnings per share	6 Months Ended
	Sep. 30, 2018
Earnings per share [abstract]
Earnings per share	Earnings per share Earnings per share, excluding exceptional items and remeasurements, are provided to reflect the business performance subtotals used by the Group, as set out in note 1. For further details of exceptional items and remeasurements, see note 4. The earnings per share calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests. (a) Basic earnings per share Six months ended 30 September 2018 2018 2017¹ 2017¹ Earnings Earnings per share Earnings Earnings per share £m Pence £m Pence Profit after tax before exceptional items and remeasurements - continuing 598 17.8 587 16.6 Exceptional items and remeasurements after tax - continuing (170 ) (5.1 ) 39 1.1 Profit after tax from continuing operations attributable to the parent 428 12.7 626 17.7 Profit after tax before exceptional items and remeasurements - discontinued 48 1.4 67 1.9 Exceptional items and remeasurements after tax - discontinued (45 ) (1.3 ) (17 ) (0.5 ) Profit after tax from discontinued operations attributable to the parent 3 0.1 50 1.4 Total profit after tax before exceptional items and remeasurements 646 19.2 654 18.5 Total exceptional items and remeasurements after tax (215 ) (6.4 ) 22 0.6 Total profit after tax attributable to the parent 431 12.8 676 19.1 Millions Millions Weighted average number of shares - basic 2 3,367 3,539 (b) Diluted earnings per share Six months ended 30 September 2018 2018 2017¹ 2017¹ Earnings Earnings per share Earnings Earnings per share £m Pence £m Pence Profit after tax before exceptional items and remeasurements - continuing 598 17.7 587 16.5 Exceptional items and remeasurements after tax - continuing (170 ) (5.1 ) 39 1.1 Profit after tax from continuing operations attributable to the parent 428 12.6 626 17.6 Profit after tax before exceptional items and remeasurements - discontinued 48 1.4 67 1.9 Exceptional items and remeasurements after tax - discontinued (45 ) (1.3 ) (17 ) (0.5 ) Profit after tax from discontinued operations attributable to the parent 3 0.1 50 1.4 Total profit after tax before exceptional items and remeasurements 646 19.1 654 18.4 Total exceptional items and remeasurements after tax (215 ) (6.4 ) 22 0.6 Total profit after tax attributable to the parent 431 12.7 676 19.0 Millions Millions Weighted average number of shares - diluted 2 3,381 3,554 1. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6). 2. The weighted average number of shares for the six month period ended 30 September 2017 includes the effect of the share consolidation, special dividend and share buy-back programme that took place in the three month period following the sale of the UK Gas Distribution business on 31 March 2017, as described in the Annual Report and Accounts.

Dividends

Dividends	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Dividends	Dividends Pence per share Cash dividend paid £m Scrip dividend £m Ordinary dividends Final dividend in respect of the year ended 31 March 2018 30.44 710 319 Special dividend - June 2017 84.375 3,171 — Final dividend in respect of the year ended 31 March 2017 29.10 970 33 The Directors are proposing an interim dividend of 16.08 p per share to be paid in respect of the year ending 31 March 2019 . This would absorb approximately £547m of shareholders’ equity. An interim dividend for the year ended 31 March 2018 of 15.49 p per share was paid in January 2018. The cash dividend paid was £346m with an additional £176m settled via a scrip issue.

Fair value measurement

Fair value measurement	6 Months Ended
	Sep. 30, 2018
Fair Value Measurement [Abstract]
Fair value measurement	Fair value measurement Assets and liabilities measured at fair value Certain of the Group's assets and liabilities are measured at fair value. The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 163 of the Annual Report and Accounts. 30 September 2018 31 March 2018 Level 1 £m Level 2 £m Level 3 £m Total £m Level 1 £m Level 2 £m Level 3 £m Total £m Assets Available-for-sale investments 1 — — — — 2,406 310 5 2,721 Investments held at FVTPL 1,194 — 25 1,219 — — — — Investments held at FVTOCI 108 338 — 446 — — — — Investments in associates 2 — — 87 87 — — 79 79 Financing derivatives — 1,246 1 1,247 — 1,544 1 1,545 Commodity contract derivatives — 18 83 101 — 8 61 69 Further Acquisition Agreement derivative 3 — — — — — — 110 110 1,302 1,602 196 3,100 2,406 1,862 256 4,524 Liabilities Financing derivatives — (828 ) (194 ) (1,022 ) — (725 ) (220 ) (945 ) Commodity contract derivatives — (33 ) (80 ) (113 ) — (54 ) (62 ) (116 ) Liabilities held at fair value (645 ) — — (645 ) — — — — (645 ) (861 ) (274 ) (1,780 ) — (779 ) (282 ) (1,061 ) Total 657 741 (78 ) 1,320 2,406 1,083 (26 ) 3,463 1. With effect from 1 April 2018 and the adoption of IFRS 9, the available-for-sale investments have been reclassified to investments held at fair value through profit and loss (FVTPL) or investments held at fair value through other comprehensive income (FVTOCI). See note 17. 2. Our level 3 investments include investments relating to Sunrun Neptune 2016 LLC accounted for at FVTPL. 3. The Group is party to the Further Acquisition Agreement (FAA) and Remaining Acquisition Agreement (RAA) which contain put and call options over 14% and 25% respectively, of the loan and equity it holds in Cadent (through its investment in Quadgas HoldCo Limited). The fair value of the FAA was deemed to be £110m at 31 March 2018. See note 6 for further details. The estimated fair value of total borrowings using market values at 30 September 2018 is £30,466m ( 31 March 2018 : £30,164m ). Our level 1 financial investments and liabilities held at fair value are valued using quoted prices from liquid markets. Our level 2 financial investments held at fair value are valued using quoted prices for similar instruments in active markets, or quoted prices for identical or similar instruments in inactive markets. Alternatively, they are valued using models where all significant inputs are based directly or indirectly on observable market data. 10. Fair value measurement (continued) Our level 2 derivative financial instruments include cross-currency, interest rate and foreign exchange derivatives. We value our level 2 derivatives by discounting all future cash flows by externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties. These derivatives can be priced using liquidly traded interest rate curves and foreign exchange rates, therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 2 commodity derivatives include over-the-counter (OTC) gas swaps and power swaps as well as forward physical gas deals. We value our contracts based on market data obtained from the New York Mercantile Exchange (NYMEX) and the Intercontinental Exchange (ICE) where monthly prices are available. We discount based on externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties and liquidity in the market. Our commodity contracts can be priced using liquidly traded swaps, therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 3 derivative financial instruments include cross-currency swaps, inflation linked swaps and equity options, all of which are traded on illiquid markets. In valuing these instruments we use in-house valuation models and obtain external valuations to support each reported fair value. In addition we also use internally developed models to value Limited Price Index (LPI) derivatives where the inflation curve is illiquid. Inputs include breakeven rates and inflation option premiums which are increasingly illiquid, towards the long-dated points on the curve. Our level 3 commodity contract derivatives primarily consist of our forward purchases of electricity and gas where pricing inputs are unobservable, as well as other complex transactions. Complex transactions can introduce the need for internally developed models based on reasonable assumptions. Industry standard valuation techniques such as the Black-Scholes pricing model and Monte Carlo simulation are used for valuing such instruments. Level 3 is also applied in cases when optionality is present or where an extrapolated forward curve is considered unobservable. All published forward curves are verified to market data; if forward curves differ from market data by 5% or more they are considered unobservable. Our level 3 investment in Sunrun Neptune 2016 LLC is fair valued by discounting expected cashflows using a weighted average cost of capital specific to Sunrun Neptune 2016 LLC. The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives within net debt (see note 11) Commodity contract derivatives Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m 10% increase in commodity prices — — 1 (2 ) 10% decrease in commodity prices — — (2 ) 2 +10% market area price change — — (8 ) (7 ) -10% market area price change — — 7 5 +20 basis point increase in Limited Price Index (LPI) market curve 1 (81 ) (85 ) — — -20 basis point decrease in LPI market curve 1 79 82 — — 1. A reasonably possible change in assumption of other level 3 derivative financial instruments is unlikely to result in a material change in fair values. The impacts disclosed above were considered on a contract by contract basis with the most significant unobservable inputs identified. For our level 3 investments, the sensitivity of the fair value of our investment in Sunrun Neptune 2016 LLC, using a 50 basis point increase/decrease in the discount rate would decrease/increase the fair value by £(4) million / £4 million (2017: £(4) million / £4 million ) respectively. The additional investments categorised as level 3 were acquired in the period on market terms and sensitivity is considered insignificant at 30 September 2018 . 10. Fair value measurement (continued) The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives within net debt (see note 11) Commodity contract derivatives Other 3 2018 2017 2018 2017 2018⁴ 2017⁴ £m £m £m £m £m £m At 1 April (219 ) (465 ) (1 ) (16 ) 194 46 Net gains/(losses) through the consolidated income statement for the period 1, 2 26 8 (16 ) (1 ) 4 (2 ) Net gains through other comprehensive income for the period — — — — 6 — Transfer to held for sale — — — — (110 ) — Purchases — — 6 — 21 35 Settlements — 231 13 26 (2 ) — At 30 September (193 ) (226 ) 2 9 113 79 1. Gains of £26m ( 2017 : gains of £5m ) are attributable to derivative financial instruments held at the end of the reporting period. 2. Losses of £11m ( 2017 : losses of £1m ) are attributable to commodity contract derivative financial instruments held at the end of the reporting period. 3. Other comprises our investments in Sunrun Neptune 2016 LLC and Embala and the investments made by the Group Technology and Innovation function, which are accounted for at fair value through profit and loss. In addition, the opening balance also includes the Further Acquisition Agreement and Remaining Acquisition Agreement derivatives of £110m that were recognised at 31 March 2018, and have been subsequently reclassified to held for sale (see note 6). 4. There were no reclassifications out of level 3 ( 2017 : none ).

Net debt

Net debt	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Net debt	Net debt Net debt comprises our cash and cash equivalents, borrowings and any derivatives thereon (financing derivatives). It also includes current financial investments. Net debt excludes commodity contract derivatives and the derivatives associated with our interest in Quadgas (see note 6). 30 September 2018 31 March 2018 £m £m Cash, cash equivalents and current financial investments 1,788 3,023 Borrowings and bank overdrafts (27,644 ) (26,625 ) Financing derivatives 1 225 600 Net debt (net of related derivative financial instruments) (25,631 ) (23,002 ) 1. Includes £ 76 m ( 2017 : £67m ) in relation to capital expenditure. The cash flows for these derivatives are included within investing activities and not financing activities in the consolidated cash flow statement. The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2018 31 March 2018 Assets Liabilities Total Assets Liabilities Total £m £m £m £m £m £m Financing derivatives 1,247 (1,022 ) 225 1,545 (945 ) 600 Commodity contract derivatives 101 (113 ) (12 ) 69 (116 ) (47 ) Further Acquisition Agreement derivative — — — 110 — 110 Total derivative financial instruments 1,348 (1,135 ) 213 1,724 (1,061 ) 663 Analysis of changes in net debt Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2018 329 2,694 (26,625 ) 600 (23,002 ) Impact of transition to IFRS 9 — — (32 ) — (32 ) At 1 April 2018 (as restated) 329 2,694 (26,657 ) 600 (23,034 ) Cash flows 1 (202 ) (1,171 ) 424 260 (689 ) Fair value gains and losses and exchange movements 3 95 (851 ) (620 ) (1,373 ) Interest income/(charge) 2 — 16 (540 ) (15 ) (539 ) Other non-cash movements — 24 (20 ) — 4 30 September 2018 130 1,658 (27,644 ) 225 (25,631 ) Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2017 1,139 8,741 (28,638 ) (516 ) (19,274 ) Cash flows (1,099 ) (6,148 ) 2,592 144 (4,511 ) Fair value gains and losses and exchange movements (1 ) (40 ) 522 789 1,270 Interest income/(charge) 2 — 20 (546 ) 5 (521 ) Other non-cash movements — — (39 ) — (39 ) 30 September 2017 39 2,573 (26,109 ) 422 (23,075 ) 1. Cash flows excludes £17m (2017: £ nil ) interest received in relation to a litigation settlement, which is included within interest received within investing activities in the consolidated cash flow statement. 2. Exceptional income of £ nil ( 2017 : £3m ) is included in net interest charge on the components of net debt and an exceptional cash inflow of £ nil ( 2017 : £3m ) is included in net interest paid on the components of net debt.

Analysis of changes in net debt

Analysis of changes in net debt	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Analysis of changes in net debt	Net debt Net debt comprises our cash and cash equivalents, borrowings and any derivatives thereon (financing derivatives). It also includes current financial investments. Net debt excludes commodity contract derivatives and the derivatives associated with our interest in Quadgas (see note 6). 30 September 2018 31 March 2018 £m £m Cash, cash equivalents and current financial investments 1,788 3,023 Borrowings and bank overdrafts (27,644 ) (26,625 ) Financing derivatives 1 225 600 Net debt (net of related derivative financial instruments) (25,631 ) (23,002 ) 1. Includes £ 76 m ( 2017 : £67m ) in relation to capital expenditure. The cash flows for these derivatives are included within investing activities and not financing activities in the consolidated cash flow statement. The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2018 31 March 2018 Assets Liabilities Total Assets Liabilities Total £m £m £m £m £m £m Financing derivatives 1,247 (1,022 ) 225 1,545 (945 ) 600 Commodity contract derivatives 101 (113 ) (12 ) 69 (116 ) (47 ) Further Acquisition Agreement derivative — — — 110 — 110 Total derivative financial instruments 1,348 (1,135 ) 213 1,724 (1,061 ) 663 Analysis of changes in net debt Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2018 329 2,694 (26,625 ) 600 (23,002 ) Impact of transition to IFRS 9 — — (32 ) — (32 ) At 1 April 2018 (as restated) 329 2,694 (26,657 ) 600 (23,034 ) Cash flows 1 (202 ) (1,171 ) 424 260 (689 ) Fair value gains and losses and exchange movements 3 95 (851 ) (620 ) (1,373 ) Interest income/(charge) 2 — 16 (540 ) (15 ) (539 ) Other non-cash movements — 24 (20 ) — 4 30 September 2018 130 1,658 (27,644 ) 225 (25,631 ) Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2017 1,139 8,741 (28,638 ) (516 ) (19,274 ) Cash flows (1,099 ) (6,148 ) 2,592 144 (4,511 ) Fair value gains and losses and exchange movements (1 ) (40 ) 522 789 1,270 Interest income/(charge) 2 — 20 (546 ) 5 (521 ) Other non-cash movements — — (39 ) — (39 ) 30 September 2017 39 2,573 (26,109 ) 422 (23,075 ) 1. Cash flows excludes £17m (2017: £ nil ) interest received in relation to a litigation settlement, which is included within interest received within investing activities in the consolidated cash flow statement. 2. Exceptional income of £ nil ( 2017 : £3m ) is included in net interest charge on the components of net debt and an exceptional cash inflow of £ nil ( 2017 : £3m ) is included in net interest paid on the components of net debt.

Pensions and other post-retirem

Pensions and other post-retirement benefit obligations	6 Months Ended
	Sep. 30, 2018
Employee Benefits [Abstract]
Pensions and other post-retirement benefit obligations	Pensions and other post-retirement benefit obligations 30 September 2018 31 March 2018 £m £m Present value of funded obligations (23,601 ) (23,747 ) Fair value of plan assets 24,307 23,858 706 111 Present value of unfunded obligations (318 ) (307 ) Other post-employment liabilities (58 ) (67 ) Net asset/(liability) 330 (263 ) Presented in consolidated statement of financial position: Liabilities (1,424 ) (1,672 ) Assets 1,754 1,409 Net asset/(liability) 330 (263 ) Key actuarial assumptions 30 September 2018 31 March 2018 Discount rate - UK past service 2.85 % 2.60 % Discount rate - US 4.25 % 4.00 % Rate of increase in RPI - past service 3.25 % 3.15 % The net pensions and other post-retirement benefit obligations position, as recorded under IAS19, at 30 September 2018 was an asset of £330m compared to a liability of £263m at 31 March 2018 . The movement of £593m primarily reflects changes in actuarial assumptions resulting in a reduction in liabilities, asset performance being less than the discount rate, and employer contributions paid over the accounting period. 13. Pensions and other post-retirement benefit obligations (continued) Changes in actuarial assumptions, primarily movements in discount rates, led to a reduction in liabilities of £703m (a decrease in UK and US liabilities of £359m and £344m respectively) which reflected increases in corporate bond yields in both the UK and US. A loss of £135m reflects returns on assets, primarily in the UK, being less than the discount rate. The net impact of actuarial gains and losses has been reflected within the consolidated statement of comprehensive income. Employer contributions of £242m were paid over the accounting period. The pension surpluses in both the UK in relation to the National Grid UK Pension Scheme of £1,277m ( 31 March 2018 : £1,105m ) and the National Grid Electricity Group of the Electricity Supply Scheme of £209m (31 March 2018: £73m ) and the Niagara Mohawk Plan in the US of £268m ( 31 March 2018 : £231m ) continue to be recognised as assets under IFRIC 14 as explained on page 146 of the Annual Report and Accounts. The pension surplus at 30 September 2018 attributable to the UK pension plans do not reflect any accounting consequences that may be required as a result of guaranteed minimum pension equalisation. We will be considering the consequences of the recent Lloyds Banking Group judgement issued by the High Court in the coming months.

Commitments and contingencies

Commitments and contingencies	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Commitments and contingencies	Commitments and contingencies At 30 September 2018 , there were commitments for future capital expenditure contracted but not provided for of £1,851m ( 2017 : £2,148m ). We also have other commitments relating primarily to commodity purchase contracts, operating leases and contingencies in the form of certain guarantees and letters of credit. Other than the repayment of the Guaranteed Notes (described in note 18), these commitments and contingencies are described in further detail on page 157 of the Annual Report and Accounts. In October 2018, the High Court handed down a judgement involving the Lloyds Banking Group's defined benefit pension schemes, concluding that the schemes should equalise benefits for men and women in relation to guaranteed minimum pension benefits. See note 13 above for further details. Litigation and claims Through the ordinary course of our operations, we are party to various litigation, claims and investigations. We do not expect the ultimate resolution of any of these proceedings to have a material adverse effect on our results of operations, cash flows or financial position.

Exchange rates

Exchange rates	6 Months Ended
	Sep. 30, 2018
Foreign exchange rates [abstract]
Exchange rates	Exchange rates The consolidated results are affected by the exchange rates used to translate the results of our US operations and US dollar transactions. The US dollar to pound sterling exchange rates used were: 30 September 2018 2017 Year Ended 31 March 2018 Closing rate applied at period end 1.30 1.34 1.40 Average rate applied for the period 1.31 1.31 1.36

Related party transactions

Related party transactions	6 Months Ended
	Sep. 30, 2018
Related Party [Abstract]
Related party transactions	Related party transactions Related party transactions in the six months ended 30 September 2018 were substantially the same in nature to those disclosed on page 158 of the Annual Report and Accounts. We continue to treat Quadgas as a related party as we still own 39% . There were no related party transactions in the period that have materially affected the financial position or performance of the Group.

Transition to IFRS 9 and IFRS 1

Transition to IFRS 9 and IFRS 15	6 Months Ended
	Sep. 30, 2018
Disclosure of comparative information prepared under previous GAAP [abstract]
Transition to IFRS 9 and IFRS 15	Transition to IFRS 9 and IFRS 15 The Group has adopted IFRS 9 and IFRS 15 prospectively, with effect from 1 April 2018 . The impact of the transition on the opening consolidated statement of financial position are set out in the following table: Impact of transition 31 March 2018 Transition adjustments 1 April 2018 IFRS 9 IFRS 15 £m £m £m £m Non-current assets Goodwill 5,444 — — 5,444 Other intangible assets 899 — — 899 Property, plant and equipment 39,853 — — 39,853 Other non-current assets 115 — — 115 Pension assets 1,409 — — 1,409 Financial and other investments 899 — — 899 Investments in joint ventures and associates 2,168 — — 2,168 Derivative financial assets 1,319 — — 1,319 Total non-current assets 52,106 — — 52,106 Current assets Inventories and current intangible assets 341 — — 341 Trade and other receivables 2,798 — (3 ) 2,795 Current tax assets 114 — 2 116 Financial and other investments 2,694 — — 2,694 Derivative financial assets 405 — — 405 Cash and cash equivalents 329 — — 329 Total current assets 6,681 — (1 ) 6,680 Total assets 58,787 — (1 ) 58,786 Current liabilities Borrowings (4,447 ) — — (4,447 ) Derivative financial liabilities (401 ) — — (401 ) Trade and other payables (3,453 ) — 27 ⁷ (3,426 ) Contract liabilities — — (21 )⁷ (21 ) Current tax liabilities (123 ) — — (123 ) Provisions (273 ) — — (273 ) Total current liabilities (8,697 ) — 6 (8,691 ) Non-current liabilities Borrowings (22,178 ) (32 )³ — (22,210 ) Derivative financial liabilities (660 ) — — (660 ) Other non-current liabilities (1,317 ) — 530 ⁷ (787 ) Contract liabilities — — (776 )⁷ (776 ) Deferred tax liabilities (3,636 ) 5 ⁴ 72 ⁸ (3,559 ) Pensions and other post-retirement benefit obligations (1,672 ) — — (1,672 ) Provisions (1,779 ) — — (1,779 ) Total non-current liabilities (31,242 ) (27 ) (174 ) (31,443 ) Total liabilities (39,939 ) (27 ) (168 ) (40,134 ) Net assets 18,848 (27 ) (169 ) 18,652 Equity Share capital 452 — — 452 Share premium account 1,321 — — 1,321 Retained earnings 21,599 (99 )⁵ (169 )⁹ 21,331 Other equity reserves (4,540 ) 72 ⁶ — (4,468 ) Total shareholders’ equity 18,832 (27 ) (169 ) 18,636 Non-controlling interests 16 — — 16 Total equity 18,848 (27 ) (169 ) 18,652 17. Transition to IFRS 9 and IFRS 15 (continued) Both standards were applied using the modified retrospective approach whereby comparative amounts have not been restated but a cumulative adjustment has been made to retained earnings in the 1 April 2018 opening consolidated statement of financial position. IFRS 9: Financial Instruments IFRS 9 has changed the accounting for the classification and measurement of financial instruments, impairment of financial assets, and hedge accounting. A summary of the accounting changes was provided in the Annual Report and Accounts for the year ended 31 March 2018 and the details are set out below. Adjustments arising as a result of the transition to IFRS 9: 1. The available-for-sale category has been replaced with investments held at fair value through profit and loss and investments held at fair value through other comprehensive income. The changes to the classification and measurement of financial assets have not altered the carrying value of any financial assets held by the Group. The Group has reclassified its investments based on their contractual cash flows and the business model they are held under. The insurance company fund investments and Group investments in money market funds were reclassified from available-for-sale to fair value through profit and loss as their contractual cash flows are not solely payments of principal and interest. Other investments were reclassified to fair value through other comprehensive income as they are held both to collect contractual cash flows and to sell them. The net impact to retained earnings of the reclassification on transition was an £8m gain. 2. The change from the incurred loss impairment model of IAS 39 to the expected loss model in IFRS 9 has not had a material impact on the Group’s credit loss provision. The Group calculates its impairment provision on trade receivables using a sophisticated provisions matrix. The inclusion of forward looking information has not had a significant impact on the matrix as the relevant short-term future economic conditions affecting our retail customers are expected to be similar to recent experience. 3. The Group elected to reclassify an existing liability with a carrying value of £570m from amortised cost to fair value through profit and loss to reduce a measurement mismatch. At transition, the resultant impacts include an increase in the carrying value of the liability of £32m , a reduction in retained earnings of £40m and the establishment of an own credit reserve (within Other equity reserves) of £7m . 4. Deferred tax is recognised on the adjustments recorded on the transition to IFRS 9. Reserve impacts are stated net of related deferred tax. 5. Retained earnings includes the impact from the changes to adjustments 1, 3 and 6. 6. The Group has adopted the hedge accounting requirements of IFRS 9 which more closely align with the Group’s risk management policies. On transition, it was concluded that all IAS 39 hedge relationships are qualifying IFRS 9 relationships with the treatment of the cost of hedging being the main change. The effect was a reclassification in reserves of a £67m gain from retained earnings and a £10m gain from the cash flow hedge reserve, into a new cost of hedging reserve (within Other equity reserves). In this reserve, qualifying unrealised gains and losses excluded from hedging relationships are deferred and released systematically into profit or loss to match the timing of hedged items. 17. Transition to IFRS 9 and IFRS 15 (continued) IFRS 15: Revenue from Contracts with Customers IFRS 15 has primarily changed the accounting for our connection and diversion revenues in our regulated businesses. The accounting for revenue under IFRS 15 does not represent a substantive change from the Group’s previous practice under IAS 18 for recognising revenue from sales to customers with the exception of the following items: • Certain pass-through revenues (principally revenues collected on behalf of the Scottish and Offshore transmission operators) will be recorded net of operating costs, whereas previously they were recognised gross of operating costs. Had we not adopted IFRS 15, our revenues and operating costs for the six months ended 30 September 2018 would have been £570m higher, with no impact to operating profits. • Contributions for capital works relating to connections for our customers are now deferred as contract liabilities on our consolidated statement of financial position and released over the life of the connection asset. This is a change for our US Regulated business and our UK Gas Transmission business, where previously revenues were recorded once the work was completed. Had we not adopted IFRS 15, our revenues and operating profit for the six months ended 30 September 2018 would have been £23m higher. • In the UK, contributions for capital works relating to diversions are now recognised as the works are completed. This is a change for the UK regulated businesses where revenues were previously deferred over the life of the asset. Had we not adopted IFRS 15, our revenues and operating profit for the six months ended 30 September 2018 would have been £6m lower. Adjustments arising as a result of the transition to IFRS 15: 7. Deferred income from contributions for capital works have now been reclassified to contract liabilities. In addition, these liabilities for capital works relating to connections have increased as these capital contributions for connections are cumulatively adjusted for on 1 April 2018 and are now deferred and released over the life of the connection assets. This is a change for our US Regulated business and our UK Gas Transmission business where previously revenues were recorded once the work was completed. Partially offsetting the increase in contract liabilities for connections is the change in accounting treatment for contributions relating to diversions in our UK businesses. These contributions are recognised as revenue as the works are completed where previously revenue was recognised over the life of the asset. 8. Deferred tax is recorded on the incremental amounts recorded against capital contributions and contract liabilities on the transition to IFRS 15. Deferred tax balances have been calculated at the rate substantially enacted at the balance sheet date. 9. The transition adjustment reflects the net of the above.

Additional disclosures in respe

Additional disclosures in respect of guaranteed securities	6 Months Ended
	Sep. 30, 2018
Separate Financial Statements [Abstract]
Additional disclosures in respect of guaranteed securities	Additional disclosures in respect of guaranteed securities On 1 June 2018, the Group repaid the 6.625% Guaranteed Notes due 2018 that were issued in June 1998 by British Transco Finance Inc., then known as British Gas Finance Inc. (issuer of notes). As a result, at 30 September 2018 , the only debt issuances (including preferred shares) that are listed on a US national securities exchange and are guaranteed by other companies in the Group are Niagara Mohawk Power Corporation’s 3.6% and 3.9% issued preferred shares, which amount to £29m . National Grid plc provided a guarantee, dated 29 October 2007 for these preferred shares. National Grid plc’s guarantee of Niagara Mohawk Power Corporation’s preferred shares is full and unconditional pursuant to Rule 3-10(i)(8) (i) and (ii) of Regulation S-X. These guarantors commit to honour any liabilities should the company issuing the debt have any financial difficulties. In order to provide debt holders with information on the financial stability of the companies providing the guarantees, we are required to disclose individual financial information for these companies. Summary statements of comprehensive income and summary cash flow statements are presented, on a consolidated basis, for the period ended 30 September 2018 , with comparatives also provided on the same basis. Summary statements of comprehensive income and summary cash flow statements of National Grid plc are presented under IFRS measurement principles, as modified by the inclusion of the results of subsidiary undertakings on the basis of equity accounting principles. The summary statements of financial position of National Grid plc include the investments in subsidiaries recorded on the basis of equity accounting principles for the purposes of presenting condensed consolidating financial information under IFRS. The summary statements of financial position present these investments within non-current financial and other investments. The consolidation adjustments column includes the necessary amounts to eliminate the intercompany balances and transactions between National Grid plc, Niagara Mohawk Power Corporation and other subsidiaries. Summary statements of comprehensive income for the six months ended 30 September 2018 : Parent guarantor Issuer of Shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Continuing operations Revenue — 1,149 5,198 — 6,347 Operating costs — (958 ) (4,372 ) — (5,330 ) Total operating profit — 191 826 — 1,017 Net finance costs (109 ) (58 ) (353 ) — (520 ) Interest in equity accounted affiliates 517 — (36 ) (456 ) 25 Profit before tax 408 133 437 (456 ) 522 Tax 22 (33 ) (82 ) — (93 ) Profit after tax from continuing operations 430 100 355 (456 ) 429 Profit after tax from discontinued operations — — 3 — 3 Total profit for the period (continuing and discontinued) 430 100 358 (456 ) 432 Amounts recognised in other comprehensive income from continuing operations 1 899 79 416 (495 ) 899 Amounts recognised in other comprehensive income from discontinued operations 1 36 — — — 36 Total comprehensive income for the year 1,365 179 774 (951 ) 1,367 Attributable to: Equity shareholders 1,365 179 772 (951 ) 1,365 Non-controlling interests — — 2 — 2 1,365 179 774 (951 ) 1,367 1. Includes other comprehensive income relating to interest in equity accounted affiliates. 18. Additional disclosures in respect of guaranteed securities (continued) Summary statements of comprehensive income for the six months ended 30 September 2017: Parent guarantor Issuer of Shares National Grid plc Niagra Mohawk Power Corporation Other subsidiaries Consolidation adjustments National Grid consolidated £m £m £m £m £m Continuing operations Revenue — 1,153 5,531 — 6,684 Operating costs — (870 ) (4,540 ) — (5,410 ) Total operating profit — 283 991 — 1,274 Net finance income/(costs) 81 (52 ) (543 ) — (514 ) Dividends receivable 150 — — (150 ) — Interest in equity accounted affiliates 461 — 5 (446 ) 20 Profit before tax 692 231 453 (596 ) 780 Tax (15 ) (87 ) (51 ) — (153 ) Profit after tax from continuing operations 677 144 402 (596 ) 627 Profit after tax from discontinued operations — — 50 — 50 Profit for the year 677 144 452 (596 ) 677 Amounts recognised in other comprehensive income from continuing operations 1 255 — 517 (517 ) 255 Amounts recognised in other comprehensive income from discontinued operations 1 64 — — — 64 Total comprehensive income for the year 996 144 969 (1,113 ) 996 Attributable to: Equity shareholders 996 144 969 (1,113 ) 996 Non-controlling interests — — — — — 996 144 969 (1,113 ) 996 1. Includes other comprehensive income relating to interest in equity accounted affiliates. 18. Additional disclosures in respect of guaranteed securities (continued) Summary statements of financial position as at 30 September 2018: Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Non-current assets Goodwill — 743 5,117 — 5,860 Other intangible assets — 3 987 — 990 Property, plant and equipment — 6,769 35,892 — 42,661 Other non-current assets 9 6 90 (9 ) 96 Amounts owed by subsidiary undertakings 352 — 2,109 (2,461 ) — Pension assets — 268 1,486 — 1,754 Financial and other investments 22,983 34 3,779 (25,513 ) 1,283 Derivative financial assets 8 6 1,145 — 1,159 Total non-current assets 23,352 7,829 50,605 (27,983 ) 53,803 Current assets Inventories and current intangible assets — 61 379 — 440 Trade and other receivables — 574 1,761 — 2,335 Current tax assets — — 298 (209 ) 89 Amounts owed by subsidiary undertakings 12,710 84 13,949 (26,743 ) — Financial and other investments 718 2 938 — 1,658 Derivative financial assets 546 11 99 (467 ) 189 Cash and cash equivalents 67 3 60 — 130 Assets held for sale — — 2,121 — 2,121 Total current assets 14,041 735 19,605 (27,419 ) 6,962 Total assets 37,393 8,564 70,210 (55,402 ) 60,765 Current liabilities Borrowings (832 ) (625 ) (2,677 ) — (4,134 ) Derivative financial liabilities (58 ) (6 ) (758 ) 467 (355 ) Trade and other payables (64 ) (323 ) (2,757 ) — (3,144 ) Contract liabilities — — (26 ) — (26 ) Amounts owed to subsidiary undertakings (14,000 ) (36 ) (12,707 ) 26,743 — Current tax liabilities — (217 ) (129 ) 209 (137 ) Provisions — (20 ) (359 ) — (379 ) Liabilities held for sale — — (50 ) — (50 ) Total current liabilities (14,954 ) (1,227 ) (19,463 ) 27,419 (8,225 ) Non-current liabilities Borrowings (782 ) (1,667 ) (21,061 ) — (23,510 ) Derivative financial liabilities (232 ) (6 ) (542 ) — (780 ) Other non-current liabilities — (472 ) (396 ) — (868 ) Contract liabilities — — (834 ) — (834 ) Amounts owed to subsidiary undertakings (2,108 ) — (353 ) 2,461 — Deferred tax liabilities — (694 ) (3,217 ) 9 (3,902 ) Pensions and other post-retirement benefit obligations — (757 ) (667 ) — (1,424 ) Provisions — (280 ) (1,607 ) — (1,887 ) Total non-current liabilities (3,122 ) (3,876 ) (28,677 ) 2,470 (33,205 ) Total liabilities (18,076 ) (5,103 ) (48,140 ) 29,889 (41,430 ) Net assets 19,317 3,461 22,070 (25,513 ) 19,335 Equity Share capital 457 144 180 (324 ) 457 Share premium account 1,316 2,362 9,032 (11,394 ) 1,316 Retained earnings 21,587 954 12,732 (13,686 ) 21,587 Other equity reserves (4,043 ) 1 108 (109 ) (4,043 ) Shareholders’ equity 19,317 3,461 22,052 (25,513 ) 19,317 Non-controlling interests — — 18 — 18 Total equity 19,317 3,461 22,070 (25,513 ) 19,335 18. Additional disclosures in respect of guaranteed securities (continued) Summary statements of financial position as at 31 March 2018: Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Non-current assets Goodwill — 691 4,753 — 5,444 Other intangible assets — 3 896 — 899 Property, plant and equipment — 6,148 33,705 — 39,853 Other non-current assets — 3 112 — 115 Amounts owed by subsidiary undertakings 350 — 2,092 (2,442 ) — Pension assets — 231 1,178 — 1,409 Financial and other investments 21,708 30 5,221 (23,892 ) 3,067 Derivative financial assets 18 2 1,299 — 1,319 Total non-current assets 22,076 7,108 49,256 (26,334 ) 52,106 Current assets Inventories and current intangible assets — 36 305 — 341 Trade and other receivables — 515 2,283 — 2,798 Current tax assets — — 307 (193 ) 114 Amounts owed by subsidiary undertakings 11,253 130 11,777 (23,160 ) — Financial and other investments 939 15 1,740 — 2,694 Derivative financial assets 308 7 46 44 405 Cash and cash equivalents — 4 325 — 329 Total current assets 12,500 707 16,783 (23,309 ) 6,681 Total assets 34,576 7,815 66,039 (49,643 ) 58,787 Current liabilities Borrowings (779 ) (51 ) (3,617 ) — (4,447 ) Derivative financial liabilities (187 ) (36 ) (134 ) (44 ) (401 ) Trade and other payables (62 ) (318 ) (3,073 ) — (3,453 ) Amounts owed to subsidiary undertakings (11,810 ) — (11,350 ) 23,160 — Current tax liabilities — (202 ) (114 ) 193 (123 ) Provisions — (23 ) (250 ) — (273 ) Total current liabilities (12,838 ) (630 ) (18,538 ) 23,309 (8,697 ) Non-current liabilities Borrowings (773 ) (2,087 ) (19,318 ) — (22,178 ) Derivative financial liabilities (41 ) (18 ) (601 ) — (660 ) Other non-current liabilities — (281 ) (1,036 ) — (1,317 ) Amounts owed to subsidiary undertakings (2,092 ) — (350 ) 2,442 — Deferred tax liabilities — (626 ) (3,010 ) — (3,636 ) Pensions and other post-retirement benefit obligations — (765 ) (907 ) — (1,672 ) Provisions — (248 ) (1,531 ) — (1,779 ) Total non-current liabilities (2,906 ) (4,025 ) (26,753 ) 2,442 (31,242 ) Total liabilities (15,744 ) (4,655 ) (45,291 ) 25,751 (39,939 ) Net assets 18,832 3,160 20,748 (23,892 ) 18,848 Equity Share capital 452 133 180 (313 ) 452 Share premium account 1,321 2,194 9,032 (11,226 ) 1,321 Retained earnings 21,599 830 11,511 (12,341 ) 21,599 Other equity reserves (4,540 ) 3 9 (12 ) (4,540 ) Shareholders’ equity 18,832 3,160 20,732 (23,892 ) 18,832 Non-controlling interests — — 16 — 16 Total equity 18,832 3,160 20,748 (23,892 ) 18,848 18. Additional disclosures in respect of guaranteed securities (continued) Summary cash flow statements for the six month periods ended 30 September 2018 and 30 September 2017 : Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Period ended 30 September 2018 Net cash flow from operating activities – continuing operations 2 236 1,697 — 1,935 Net cash flow used in operating activities – discontinued operations — — (47 ) — (47 ) Net cash flow (used in)/from investing activities – continuing operations (265 ) (171 ) (545 ) 193 (788 ) Net cash flow from investing activities – discontinued operations — — 78 — 78 Net cash flow from/(used in) financing activities – continuing operations 330 (65 ) (1,452 ) (193 ) (1,380 ) Net cash flow from financing activities – discontinued operations — — — — — Net increase/(decrease) in cash and cash equivalents in the period 67 — (269 ) — (202 ) Period ended 30 September 2017 Net cash flow from operating activities – continuing operations 24 328 1,716 — 2,068 Net cash flow used in operating activities – discontinued operations — — (126 ) — (126 ) Net cash flow from/(used in) investing activities – continuing operations 3,193 155 596 280 4,224 Net cash flow from investing activities – discontinued operations — — 15 — 15 Net cash flow (used in)/from financing activities – continuing operations (4,303 ) (482 ) (1,984 ) (280 ) (7,049 ) Net cash flow used in financing activities – discontinued operations — — (231 ) — (231 ) Net (decrease)/increase in cash and cash equivalents in the period (1,086 ) 1 (14 ) — (1,099 )

Basis of preparation and new _2

Basis of preparation and new accounting standards, interpretations and amendments (Policies)	6 Months Ended
	Sep. 30, 2018
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Accounting policy for basis of accounting	The half year financial information covers the six month period ended 30 September 2018 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB) and as adopted by the European Union (EU); and the Disclosure and Transparency Rules of the Financial Conduct Authority. This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2018 and 2017 , together with the audited consolidated statement of financial position at 31 March 2018 . The financial information for the year ended 31 March 2018 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2018 , which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB and as adopted by the EU, and have been filed with the Registrar of Companies. The Deloitte LLP audit report on these statutory accounts was unqualified, did not contain an emphasis of matter and did not contain a statement under Section 498 of the Companies Act 2006. The half year financial information has been prepared in accordance with the accounting policies expected to be applicable for the year ending 31 March 2019 . The notes to the financial statements have been prepared on a continuing basis unless otherwise stated. The Group has adopted IFRS 9 'Financial Instruments' and IFRS 15 'Revenue from Contracts with Customers' for the first time with effect from 1 April 2018. Other than in this respect, the half year financial statements have been prepared on a basis consistent with that applied in the preparation of the financial statements for the year ended 31 March 2018 , other than as outlined below in relation to discontinued operations. Our consolidated income statement and segmental analysis (see note 2) separately identify financial results before and after exceptional items and remeasurements. The Directors believe that presentation of the results in this way is relevant to an understanding of the Group’s financial performance. Presenting financial results before exceptional items and remeasurements is consistent with the way that financial performance is measured by management and reported to the Board and Executive Committee and improves the comparability of reported financial performance from year to year. Events or transactions which are classified as exceptional items or remeasurements are defined in the Annual Report and Accounts and Form 20-F. We continue to adopt a columnar presentation as we consider it improves the clarity of the presentation, and is consistent with the way that financial performance is measured by management and reported to the Board and Executive Committee, and better enables users of the financial statements to understand the results. The inclusion of total profit for the period from continuing operations before exceptional items and remeasurements forms part of the incentive target set annually for remunerating certain Executive Directors and accordingly we believe it is important for users of the financial statements to understand how this compares to our results on a statutory basis and period on period.
Accounting policy for accounting estimates	Areas of judgement and key sources of estimation uncertainty In preparing this half year financial information, the areas where judgement has been exercised by management in applying the Group’s accounting policies and the key sources of estimation uncertainty remain consistent with those applied to the Annual Report and Accounts for the year ended 31 March 2018 . In applying the Group’s exceptional items framework for the half year, we have considered three key matters. As described further in note 4, we have concluded that the costs associated with the Massachusetts Gas work continuation ( £97m ) and the UK cost efficiency and restructuring programme ( £127m ) should be treated as exceptional. We also considered whether the £94m income from two legal settlements received in the period should also be classified as exceptional. However, we concluded it was appropriate to recognise the income in earnings before exceptional items (within Other Activities), in line with the treatment of the original costs. In addition, in preparing the half year financial information, we have exercised our judgement in concluding that it is appropriate to classify our investment in and shareholder loan to Quadgas HoldCo Limited (Quadgas), along with the related Further Acquisition Agreement (FAA) and Remaining Acquisition Agreement (RAA) derivatives, as held for sale and as a discontinued operation, as detailed in note 6.
Accounting policy for going concern	Going concern Having made enquiries and reassessed the principal risks, the Directors consider that the Company and its subsidiary undertakings have adequate resources to continue in business for the foreseeable future, being a period of not less than 12 months from the date of this report. Accordingly, it is appropriate to adopt the going concern basis in preparing the half year financial information.
Accounting policy for new accounting standards or interpretations	New IFRS accounting standards and interpretations adopted in the period The Group has adopted IFRS 9 ‘Financial Instruments’ and IFRS 15 ‘Revenue from Contracts with Customers’ for the first time with effect from 1 April 2018. Refer to note 17 for details of the impact and transition adjustments arising on adoption. There are no other new standards, interpretations and amendments, issued by the IASB or by the IFRS Interpretations Committee (IFRIC), that are applicable for the period commencing on 1 April 2018 that have had a material impact on the Group’s results. New IFRS accounting standards and interpretations not yet adopted The Group continues to assess the impact of IFRS 16 'Leases', which will be implemented on 1 April 2019. The Group enters into a significant number of operating lease transactions. Under IFRS 16, our operating leases will be accounted for on the consolidated statement of financial position as ‘right-of-use’ assets. This treatment will increase both our assets and liabilities and subsequently, will result in an increase in finance costs and depreciation and a reduction in operating costs. We continue to assess our revenue, service contracts and power purchase contracts to determine whether we have the right to use assets under those contracts and whether they fall within the scope of IFRS 16. We plan to apply IFRS 16 using the modified retrospective approach, whereby comparatives will not be restated on adoption of the new standard but instead a cumulative adjustment will be reflected in retained earnings. We will provide further details of the impact that the implementation of IFRS 16 will have in the Annual Report and Accounts for the year ending 31 March 2019. There are no new accounting standards and amendments to existing standards that have been issued, but are not yet effective or have not yet been endorsed by the EU that were not disclosed in our Annual Report and Accounts. The Group has not early adopted any standard, amendment or interpretation that has been issued but is not yet effective.

Segmental analysis (Tables)

Segmental analysis (Tables)	6 Months Ended
	Sep. 30, 2018
Operating Segments [Abstract]
Schedule of operating segments	(a) Revenue Six months ended 30 September 2018 2017 £m £m Operating segments - continuing operations: UK Electricity Transmission 1,574 2,076 UK Gas Transmission 353 422 US Regulated 4,053 3,799 NGV and Other 1 387 407 Sales between segments (20 ) (20 ) Total revenue from continuing operations 6,347 6,684 Geographical areas: UK 2,272 2,865 US 4,075 3,819 Total revenue from continuing operations 6,347 6,684 1. Included within NGV and Other is £294m ( 2017 : £294m ) of revenue relating to NGV and £44m (2017: £59m ) of revenue relating to UK property development. 2. Segmental analysis (continued) (b) Operating profit Before exceptional items and remeasurements 1 After exceptional items and remeasurements 1 Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 531 542 437 542 UK Gas Transmission 79 126 46 126 US Regulated 385 433 327 448 NGV and Other 2, 3 207 158 207 158 Total operating profit from continuing operations 1,202 1,259 1,017 1,274 Geographical areas UK 761 852 634 852 US 441 407 383 422 Total operating profit from continuing operations 1,202 1,259 1,017 1,274 Below we reconcile total operating profit to profit before tax from continuing operations. Operating exceptional items and remeasurements of £94m expense (2017: £ nil ) detailed in note 4 are attributable to UK Electricity Transmission; £33m expense (2017: £ nil ) to UK Gas Transmission; and £58m expense ( 2017 : £15m income) to US Regulated operations. Before exceptional items and remeasurements 1 After exceptional items and remeasurements 1 Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m Reconciliation to profit before tax: Operating profit - continuing operations 1,202 1,259 1,017 1,274 Share of post-tax results of joint ventures and associates 25 20 25 20 Finance income 42 24 42 24 Finance costs (536 ) (566 ) (562 ) (538 ) Profit before tax from continuing operations 733 737 522 780 1. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6). 2. Included within NGV and Other is £ 131 m ( 2017 : £132m ) of operating profit (both before and after exceptional items and remeasurements) relating to NGV and £38m (2017: £53m ) of operating profit (both before and after exceptional items and remeasurements) relating to UK property development. 3. NGV and Other includes gains of £94m (2017: £ nil ) in relation to cash received in respect of two legal settlements. 2. Segmental analysis (continued) (c) Other segmental information Net book value 1 Capital expenditure 2 Depreciation and amortisation 3 30 September 2018 31 March 30 September 2018 30 September 2017 30 September 2018 30 September 2017 £m £m £m £m £m £m Operating segments: UK Electricity Transmission 13,247 13,028 462 515 (242 ) (226 ) UK Gas Transmission 4,345 4,280 153 157 (92 ) (94 ) US Regulated 23,395 20,953 1,177 1,095 (346 ) (328 ) NGV and Other 4, 5 2,664 2,491 248 125 (111 ) (114 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) Geographical areas: UK 19,094 18,772 782 751 (399 ) (393 ) US 24,557 21,980 1,258 1,141 (392 ) (369 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) By asset type: Property, plant and equipment 42,661 39,853 1,900 1,820 (710 ) (689 ) Non-current intangible assets 990 899 140 72 (81 ) (73 ) Total from continuing operations 43,651 40,752 2,040 1,892 (791 ) (762 ) 1. Represents the net book value of property, plant and equipment and other non-current intangible assets at 30 September 2018 and 31 March 2018 respectively. 2. Represents additions to property, plant and equipment and other non-current intangibles, in the six months ended 30 September 2018 and 30 September 2017 respectively. 3. Represents the amounts recorded in the consolidated income statement for the six months ended 30 September 2018 and 30 September 2017 respectively. 4. Included within NGV and Other are assets with a net book value of £1,518m and £60m ( 31 March 2018 : £1,454m and £52m ), capital expenditures of £136 m and £11m ( 2017 : £72m and £5m ) and depreciation and amortisation of £64 m and £1m ( 2017 : £68m and £ nil ) relating to NGV and UK property development respectively. 5. Net book value for NGV and Other includes certain software assets and properties in the US which are outside the US rate base and operate for the benefit of our US regulated businesses. Costs associated with owning and operating these assets (principally depreciation and amortisation) are recharged to the US regulated business.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Sep. 30, 2018
Revenue from Contracts with Customers [Abstract]
Schedule of disaggregation of revenue from contracts with customers	Revenue for the six months ended 30 September 2018 UK Electricity Transmission £m UK Gas Transmission £m US Regulated £m NG Ventures and Other £m Total £m Revenue under IFRS 15 Transmission 1,559 322 315 152 2,348 Distribution — — 3,478 — 3,478 Other 1 — — — 138 138 Total IFRS 15 revenue 1,559 322 3,793 290 5,964 Other revenue 2 Generation — — 183 — 183 Other 3 25 77 95 200 Total other revenue 3 25 260 95 383 Total revenue from continuing operations 1,562 347 4,053 385 6,347 Geographic split of revenue for the six months ended 30 September 2018 UK Electricity Transmission £m UK Gas Transmission £m US Regulated £m NG Ventures and Other £m Total £m Revenue under IFRS 15 UK 1,559 322 — 290 2,171 US — — 3,793 — 3,793 Total IFRS 15 revenue 1,559 322 3,793 290 5,964 Other revenue UK 3 25 — 73 101 US 2 — — 260 22 282 Total other revenue 3 25 260 95 383 Total revenue from continuing operations 1,562 347 4,053 385 6,347 1. Other IFRS 15 revenue relates to revenue generated from metering businesses. 2. Other revenue principally consists of income relating to US generation contracts where we act as lessor under the leasing standard (IAS 17).

Exceptional items and remeasu_2

Exceptional items and remeasurements (Tables)	6 Months Ended
	Sep. 30, 2018
Exceptional Items And Remeasurements [Abstract]
Schedule of exceptional items and remeasurements from continuing operations	Six months ended 30 September 2018 Exceptional items Remeasurements Total £m £m £m Included within operating profit from continuing operations UK cost efficiency and restructuring programme 1 (127 ) — (127 ) Massachusetts Gas work continuation 2 (97 ) (97 ) Net gains on commodity contract derivatives 3(i) — 39 39 (224 ) 39 (185 ) Included within net finance costs (note 5) Net losses on derivative financial instruments 3(ii) — (26 ) (26 ) Net gains on FVTPL financial assets 3(iii) — 8 8 Net losses on FVTPL financial liabilities 3(iv) — (8 ) (8 ) — (26 ) (26 ) Total included within profit before tax from continuing operations (224 ) 13 (211 ) Tax 48 (7 ) 41 Total exceptional items and remeasurements after tax from continuing operations (176 ) 6 (170 ) Six months ended 30 September 2017 Exceptional items 4 Remeasurements 4 Total 4 £m £m £m Included within operating profit from continuing operations Net gains on commodity contract derivatives 3(i) — 15 15 — 15 15 Included within net finance costs (note 5) Net gains on derivative financial instruments 3(ii) — 28 28 28 28 Total included within profit before tax from continuing operations — 43 43 Tax — (4 ) (4 ) Total exceptional items and remeasurements after tax from continuing operations — 39 39 1. UK cost efficiency and restructuring programme: In July 2018, our UK business consulted on a series of significant restructuring activities relating to our core UK regulated activities in anticipation of the upcoming RIIO-T2 price control. During the period we completed a comprehensive review of the organisational structure, certain operational activities, and relevant roles and responsibilities across Electricity Transmission and Gas Transmission, with changes communicated ahead of 30 September. By 30 September 2018 we had provided over £100m associated with severance costs, with the remainder of the £127m exceptional charge relating to associated support and planning costs. We expect some further costs will be incurred during the second half of the year as we complete our transition. On the basis that this item is material for the half year results and the full year financial statements, we have treated the costs as exceptional. The cash outflow for the period was £18m . 4. Exceptional items and remeasurements (continued) 2. Massachusetts Gas work continuation: On 25 June 2018, National Grid implemented a workforce contingency plan across its Massachusetts Gas business following the expiration of contracts for the existing workforce. Since then we have employed experienced contractors alongside supervisors and workers from other areas of our business to ensure work continues safely. In view of the significance of this item to the half year results and on the basis that it will be material to the full year financial statements, we have treated the incremental direct and associated incidental costs as exceptional. As at 30 September 2018, the incremental costs totalled $127m ( £97m ). The total cash outflow related to the work continuation for the period was $134m ( £102m ). 3. Remeasurements on derivative financial instruments: i. Net gains/(losses) on commodity contract derivatives represent mark-to-market movements on certain physical and financial commodity contract obligations in the US. These contracts primarily relate to the forward purchase of energy for supply to customers, or to the economic hedging thereof, that are required to be measured at fair value and do not qualify for hedge accounting. Under the existing rate plans in the US, commodity costs are recoverable from customers although the timing of recovery may differ from the pattern of costs incurred. ii. Net gains/(losses) on derivative financial instruments comprise gains/(losses) arising on derivative financial instruments reported in the consolidated income statement in relation to our debt financing and foreign exchange hedging of the investment funds held by our insurance captives. These exclude gains and losses for which hedge accounting has been effective, and have been recognised directly in other comprehensive income or are offset by adjustments to the carrying value of debt. iii. Net gains/(losses) on fair value through profit and loss (FVTPL) financial assets comprise gains/(losses) on the investment funds held by our insurance captives and Group money market fund investments which are categorised as fair value through profit and loss (see note 17). iv. Net gains/(losses) on FVTPL financial liabilities comprises the change in the fair value (excluding changes due to own credit risk) of a financial liability that has been designated at fair value through profit and loss on transition to IFRS 9 to reduce a measurement mismatch (see note 17). 4. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Finance income and costs (Table

Finance income and costs (Tables)	6 Months Ended
	Sep. 30, 2018
Analysis of income and expense [abstract]
Schedule of Finance income and costs	Six months ended 30 September 2018 2017 Notes £m £m Finance income before exceptional items and remeasurements Interest income on financial instruments 1 42 24 42 24 Finance costs before exceptional items and remeasurements Net interest payable on pensions and other post-retirement benefit obligations (11 ) (33 ) Interest expense on financial instruments (555 ) (546 ) Unwinding of discount on provisions (35 ) (38 ) Other interest (9 ) (8 ) Less: Interest capitalised 74 59 (536 ) (566 ) Net finance costs before exceptional items and remeasurements (494 ) (542 ) Total exceptional items and remeasurements 4 (26 ) 28 Net finance costs including exceptional items and remeasurements from continuing operations (520 ) (514 ) 1. Comparatives have been re-presented to reflect the classification of £15m of interest income in respect of our loan to Quadgas as a discontinued operation in the current period (see note 6).

Earnings per share (Tables)

Earnings per share (Tables)	6 Months Ended
	Sep. 30, 2018
Earnings per share [abstract]
Schedule of Earnings per share	(a) Basic earnings per share Six months ended 30 September 2018 2018 2017¹ 2017¹ Earnings Earnings per share Earnings Earnings per share £m Pence £m Pence Profit after tax before exceptional items and remeasurements - continuing 598 17.8 587 16.6 Exceptional items and remeasurements after tax - continuing (170 ) (5.1 ) 39 1.1 Profit after tax from continuing operations attributable to the parent 428 12.7 626 17.7 Profit after tax before exceptional items and remeasurements - discontinued 48 1.4 67 1.9 Exceptional items and remeasurements after tax - discontinued (45 ) (1.3 ) (17 ) (0.5 ) Profit after tax from discontinued operations attributable to the parent 3 0.1 50 1.4 Total profit after tax before exceptional items and remeasurements 646 19.2 654 18.5 Total exceptional items and remeasurements after tax (215 ) (6.4 ) 22 0.6 Total profit after tax attributable to the parent 431 12.8 676 19.1 Millions Millions Weighted average number of shares - basic 2 3,367 3,539 (b) Diluted earnings per share Six months ended 30 September 2018 2018 2017¹ 2017¹ Earnings Earnings per share Earnings Earnings per share £m Pence £m Pence Profit after tax before exceptional items and remeasurements - continuing 598 17.7 587 16.5 Exceptional items and remeasurements after tax - continuing (170 ) (5.1 ) 39 1.1 Profit after tax from continuing operations attributable to the parent 428 12.6 626 17.6 Profit after tax before exceptional items and remeasurements - discontinued 48 1.4 67 1.9 Exceptional items and remeasurements after tax - discontinued (45 ) (1.3 ) (17 ) (0.5 ) Profit after tax from discontinued operations attributable to the parent 3 0.1 50 1.4 Total profit after tax before exceptional items and remeasurements 646 19.1 654 18.4 Total exceptional items and remeasurements after tax (215 ) (6.4 ) 22 0.6 Total profit after tax attributable to the parent 431 12.7 676 19.0 Millions Millions Weighted average number of shares - diluted 2 3,381 3,554 1. Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6). 2. The weighted average number of shares for the six month period ended 30 September 2017 includes the effect of the share consolidation, special dividend and share buy-back programme that took place in the three month period following the sale of the UK Gas Distribution business on 31 March 2017, as described in the Annual Report and Accounts.

Dividends (Tables)

Dividends (Tables)	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Schedule of Dividends	Pence per share Cash dividend paid £m Scrip dividend £m Ordinary dividends Final dividend in respect of the year ended 31 March 2018 30.44 710 319 Special dividend - June 2017 84.375 3,171 — Final dividend in respect of the year ended 31 March 2017 29.10 970 33

Fair value measurement (Tables)

Fair value measurement (Tables)	6 Months Ended
	Sep. 30, 2018
Fair Value Measurement [Abstract]
Schedule of fair value measurement of assets	The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives within net debt (see note 11) Commodity contract derivatives Other 3 2018 2017 2018 2017 2018⁴ 2017⁴ £m £m £m £m £m £m At 1 April (219 ) (465 ) (1 ) (16 ) 194 46 Net gains/(losses) through the consolidated income statement for the period 1, 2 26 8 (16 ) (1 ) 4 (2 ) Net gains through other comprehensive income for the period — — — — 6 — Transfer to held for sale — — — — (110 ) — Purchases — — 6 — 21 35 Settlements — 231 13 26 (2 ) — At 30 September (193 ) (226 ) 2 9 113 79 1. Gains of £26m ( 2017 : gains of £5m ) are attributable to derivative financial instruments held at the end of the reporting period. 2. Losses of £11m ( 2017 : losses of £1m ) are attributable to commodity contract derivative financial instruments held at the end of the reporting period. 3. Other comprises our investments in Sunrun Neptune 2016 LLC and Embala and the investments made by the Group Technology and Innovation function, which are accounted for at fair value through profit and loss. In addition, the opening balance also includes the Further Acquisition Agreement and Remaining Acquisition Agreement derivatives of £110m that were recognised at 31 March 2018, and have been subsequently reclassified to held for sale (see note 6). 4. There were no reclassifications out of level 3 ( 2017 : none ). The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 163 of the Annual Report and Accounts. 30 September 2018 31 March 2018 Level 1 £m Level 2 £m Level 3 £m Total £m Level 1 £m Level 2 £m Level 3 £m Total £m Assets Available-for-sale investments 1 — — — — 2,406 310 5 2,721 Investments held at FVTPL 1,194 — 25 1,219 — — — — Investments held at FVTOCI 108 338 — 446 — — — — Investments in associates 2 — — 87 87 — — 79 79 Financing derivatives — 1,246 1 1,247 — 1,544 1 1,545 Commodity contract derivatives — 18 83 101 — 8 61 69 Further Acquisition Agreement derivative 3 — — — — — — 110 110 1,302 1,602 196 3,100 2,406 1,862 256 4,524 Liabilities Financing derivatives — (828 ) (194 ) (1,022 ) — (725 ) (220 ) (945 ) Commodity contract derivatives — (33 ) (80 ) (113 ) — (54 ) (62 ) (116 ) Liabilities held at fair value (645 ) — — (645 ) — — — — (645 ) (861 ) (274 ) (1,780 ) — (779 ) (282 ) (1,061 ) Total 657 741 (78 ) 1,320 2,406 1,083 (26 ) 3,463 1. With effect from 1 April 2018 and the adoption of IFRS 9, the available-for-sale investments have been reclassified to investments held at fair value through profit and loss (FVTPL) or investments held at fair value through other comprehensive income (FVTOCI). See note 17. 2. Our level 3 investments include investments relating to Sunrun Neptune 2016 LLC accounted for at FVTPL. 3. The Group is party to the Further Acquisition Agreement (FAA) and Remaining Acquisition Agreement (RAA) which contain put and call options over 14% and 25% respectively, of the loan and equity it holds in Cadent (through its investment in Quadgas HoldCo Limited). The fair value of the FAA was deemed to be £110m at 31 March 2018. See note 6 for further details.
Schedule of fair value measurement of liabilities	The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 163 of the Annual Report and Accounts. 30 September 2018 31 March 2018 Level 1 £m Level 2 £m Level 3 £m Total £m Level 1 £m Level 2 £m Level 3 £m Total £m Assets Available-for-sale investments 1 — — — — 2,406 310 5 2,721 Investments held at FVTPL 1,194 — 25 1,219 — — — — Investments held at FVTOCI 108 338 — 446 — — — — Investments in associates 2 — — 87 87 — — 79 79 Financing derivatives — 1,246 1 1,247 — 1,544 1 1,545 Commodity contract derivatives — 18 83 101 — 8 61 69 Further Acquisition Agreement derivative 3 — — — — — — 110 110 1,302 1,602 196 3,100 2,406 1,862 256 4,524 Liabilities Financing derivatives — (828 ) (194 ) (1,022 ) — (725 ) (220 ) (945 ) Commodity contract derivatives — (33 ) (80 ) (113 ) — (54 ) (62 ) (116 ) Liabilities held at fair value (645 ) — — (645 ) — — — — (645 ) (861 ) (274 ) (1,780 ) — (779 ) (282 ) (1,061 ) Total 657 741 (78 ) 1,320 2,406 1,083 (26 ) 3,463 1. With effect from 1 April 2018 and the adoption of IFRS 9, the available-for-sale investments have been reclassified to investments held at fair value through profit and loss (FVTPL) or investments held at fair value through other comprehensive income (FVTOCI). See note 17. 2. Our level 3 investments include investments relating to Sunrun Neptune 2016 LLC accounted for at FVTPL. 3. The Group is party to the Further Acquisition Agreement (FAA) and Remaining Acquisition Agreement (RAA) which contain put and call options over 14% and 25% respectively, of the loan and equity it holds in Cadent (through its investment in Quadgas HoldCo Limited). The fair value of the FAA was deemed to be £110m at 31 March 2018. See note 6 for further details. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives within net debt (see note 11) Commodity contract derivatives Other 3 2018 2017 2018 2017 2018⁴ 2017⁴ £m £m £m £m £m £m At 1 April (219 ) (465 ) (1 ) (16 ) 194 46 Net gains/(losses) through the consolidated income statement for the period 1, 2 26 8 (16 ) (1 ) 4 (2 ) Net gains through other comprehensive income for the period — — — — 6 — Transfer to held for sale — — — — (110 ) — Purchases — — 6 — 21 35 Settlements — 231 13 26 (2 ) — At 30 September (193 ) (226 ) 2 9 113 79 1. Gains of £26m ( 2017 : gains of £5m ) are attributable to derivative financial instruments held at the end of the reporting period. 2. Losses of £11m ( 2017 : losses of £1m ) are attributable to commodity contract derivative financial instruments held at the end of the reporting period. 3. Other comprises our investments in Sunrun Neptune 2016 LLC and Embala and the investments made by the Group Technology and Innovation function, which are accounted for at fair value through profit and loss. In addition, the opening balance also includes the Further Acquisition Agreement and Remaining Acquisition Agreement derivatives of £110m that were recognised at 31 March 2018, and have been subsequently reclassified to held for sale (see note 6). 4. There were no reclassifications out of level 3 ( 2017 : none ).
Sensitivity analysis for types of market risk	The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives within net debt (see note 11) Commodity contract derivatives Six months ended 30 September 2018 2017 2018 2017 £m £m £m £m 10% increase in commodity prices — — 1 (2 ) 10% decrease in commodity prices — — (2 ) 2 +10% market area price change — — (8 ) (7 ) -10% market area price change — — 7 5 +20 basis point increase in Limited Price Index (LPI) market curve 1 (81 ) (85 ) — — -20 basis point decrease in LPI market curve 1 79 82 — — 1. A reasonably possible change in assumption of other level 3 derivative financial instruments is unlikely to result in a material change in fair values.

Net debt (Tables)

Net debt (Tables)	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Schedule of components of net debt	Net debt excludes commodity contract derivatives and the derivatives associated with our interest in Quadgas (see note 6). 30 September 2018 31 March 2018 £m £m Cash, cash equivalents and current financial investments 1,788 3,023 Borrowings and bank overdrafts (27,644 ) (26,625 ) Financing derivatives 1 225 600 Net debt (net of related derivative financial instruments) (25,631 ) (23,002 ) 1. Includes £ 76 m ( 2017 : £67m ) in relation to capital expenditure. The cash flows for these derivatives are included within investing activities and not financing activities in the consolidated cash flow statement.
Balance sheet allocation of derivative balances	The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2018 31 March 2018 Assets Liabilities Total Assets Liabilities Total £m £m £m £m £m £m Financing derivatives 1,247 (1,022 ) 225 1,545 (945 ) 600 Commodity contract derivatives 101 (113 ) (12 ) 69 (116 ) (47 ) Further Acquisition Agreement derivative — — — 110 — 110 Total derivative financial instruments 1,348 (1,135 ) 213 1,724 (1,061 ) 663

Analysis of changes in net de_2

Analysis of changes in net debt (Tables)	6 Months Ended
	Sep. 30, 2018
Subclassifications of assets, liabilities and equities [abstract]
Schedule of analysis of changes in net debt	Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2018 329 2,694 (26,625 ) 600 (23,002 ) Impact of transition to IFRS 9 — — (32 ) — (32 ) At 1 April 2018 (as restated) 329 2,694 (26,657 ) 600 (23,034 ) Cash flows 1 (202 ) (1,171 ) 424 260 (689 ) Fair value gains and losses and exchange movements 3 95 (851 ) (620 ) (1,373 ) Interest income/(charge) 2 — 16 (540 ) (15 ) (539 ) Other non-cash movements — 24 (20 ) — 4 30 September 2018 130 1,658 (27,644 ) 225 (25,631 ) Cash and cash equivalents Financial investments Borrowings Financing derivatives Total £m £m £m £m £m At 31 March 2017 1,139 8,741 (28,638 ) (516 ) (19,274 ) Cash flows (1,099 ) (6,148 ) 2,592 144 (4,511 ) Fair value gains and losses and exchange movements (1 ) (40 ) 522 789 1,270 Interest income/(charge) 2 — 20 (546 ) 5 (521 ) Other non-cash movements — — (39 ) — (39 ) 30 September 2017 39 2,573 (26,109 ) 422 (23,075 ) 1. Cash flows excludes £17m (2017: £ nil ) interest received in relation to a litigation settlement, which is included within interest received within investing activities in the consolidated cash flow statement. 2. Exceptional income of £ nil ( 2017 : £3m ) is included in net interest charge on the components of net debt and an exceptional cash inflow of £ nil ( 2017 : £3m ) is included in net interest paid on the components of net debt.

Pensions and other post-retir_2

Pensions and other post-retirement benefit obligations (Tables)	6 Months Ended
	Sep. 30, 2018
Employee Benefits [Abstract]
Schedule of defined benefit plan recognised in balance sheet	30 September 2018 31 March 2018 £m £m Present value of funded obligations (23,601 ) (23,747 ) Fair value of plan assets 24,307 23,858 706 111 Present value of unfunded obligations (318 ) (307 ) Other post-employment liabilities (58 ) (67 ) Net asset/(liability) 330 (263 ) Presented in consolidated statement of financial position: Liabilities (1,424 ) (1,672 ) Assets 1,754 1,409 Net asset/(liability) 330 (263 )
Schedule of defined benefit plans assumptions	Key actuarial assumptions 30 September 2018 31 March 2018 Discount rate - UK past service 2.85 % 2.60 % Discount rate - US 4.25 % 4.00 % Rate of increase in RPI - past service 3.25 % 3.15 %

Exchange rates USD to GBP forei

Exchange rates USD to GBP foreign exchange rates (Tables)	6 Months Ended
	Sep. 30, 2018
Foreign exchange rates [abstract]
Schedule of Average and Closing Foreign Exchange Rates	The US dollar to pound sterling exchange rates used were: 30 September 2018 2017 Year Ended 31 March 2018 Closing rate applied at period end 1.30 1.34 1.40 Average rate applied for the period 1.31 1.31 1.36

Transition to IFRS 9 and IFRS_2

Transition to IFRS 9 and IFRS 15 (Tables)	6 Months Ended
	Sep. 30, 2018
Disclosure of comparative information prepared under previous GAAP [abstract]
Schedule of comparative information prepared under previous GAAP	The impact of the transition on the opening consolidated statement of financial position are set out in the following table: Impact of transition 31 March 2018 Transition adjustments 1 April 2018 IFRS 9 IFRS 15 £m £m £m £m Non-current assets Goodwill 5,444 — — 5,444 Other intangible assets 899 — — 899 Property, plant and equipment 39,853 — — 39,853 Other non-current assets 115 — — 115 Pension assets 1,409 — — 1,409 Financial and other investments 899 — — 899 Investments in joint ventures and associates 2,168 — — 2,168 Derivative financial assets 1,319 — — 1,319 Total non-current assets 52,106 — — 52,106 Current assets Inventories and current intangible assets 341 — — 341 Trade and other receivables 2,798 — (3 ) 2,795 Current tax assets 114 — 2 116 Financial and other investments 2,694 — — 2,694 Derivative financial assets 405 — — 405 Cash and cash equivalents 329 — — 329 Total current assets 6,681 — (1 ) 6,680 Total assets 58,787 — (1 ) 58,786 Current liabilities Borrowings (4,447 ) — — (4,447 ) Derivative financial liabilities (401 ) — — (401 ) Trade and other payables (3,453 ) — 27 ⁷ (3,426 ) Contract liabilities — — (21 )⁷ (21 ) Current tax liabilities (123 ) — — (123 ) Provisions (273 ) — — (273 ) Total current liabilities (8,697 ) — 6 (8,691 ) Non-current liabilities Borrowings (22,178 ) (32 )³ — (22,210 ) Derivative financial liabilities (660 ) — — (660 ) Other non-current liabilities (1,317 ) — 530 ⁷ (787 ) Contract liabilities — — (776 )⁷ (776 ) Deferred tax liabilities (3,636 ) 5 ⁴ 72 ⁸ (3,559 ) Pensions and other post-retirement benefit obligations (1,672 ) — — (1,672 ) Provisions (1,779 ) — — (1,779 ) Total non-current liabilities (31,242 ) (27 ) (174 ) (31,443 ) Total liabilities (39,939 ) (27 ) (168 ) (40,134 ) Net assets 18,848 (27 ) (169 ) 18,652 Equity Share capital 452 — — 452 Share premium account 1,321 — — 1,321 Retained earnings 21,599 (99 )⁵ (169 )⁹ 21,331 Other equity reserves (4,540 ) 72 ⁶ — (4,468 ) Total shareholders’ equity 18,832 (27 ) (169 ) 18,636 Non-controlling interests 16 — — 16 Total equity 18,848 (27 ) (169 ) 18,652

Additional disclosures in res_2

Additional disclosures in respect of guaranteed securities (Tables)	6 Months Ended
	Sep. 30, 2018
Seperate Financial Statements [Abstract]
Schedule of Condensed Income Statement	Summary statements of comprehensive income for the six months ended 30 September 2018 : Parent guarantor Issuer of Shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Continuing operations Revenue — 1,149 5,198 — 6,347 Operating costs — (958 ) (4,372 ) — (5,330 ) Total operating profit — 191 826 — 1,017 Net finance costs (109 ) (58 ) (353 ) — (520 ) Interest in equity accounted affiliates 517 — (36 ) (456 ) 25 Profit before tax 408 133 437 (456 ) 522 Tax 22 (33 ) (82 ) — (93 ) Profit after tax from continuing operations 430 100 355 (456 ) 429 Profit after tax from discontinued operations — — 3 — 3 Total profit for the period (continuing and discontinued) 430 100 358 (456 ) 432 Amounts recognised in other comprehensive income from continuing operations 1 899 79 416 (495 ) 899 Amounts recognised in other comprehensive income from discontinued operations 1 36 — — — 36 Total comprehensive income for the year 1,365 179 774 (951 ) 1,367 Attributable to: Equity shareholders 1,365 179 772 (951 ) 1,365 Non-controlling interests — — 2 — 2 1,365 179 774 (951 ) 1,367 1. Includes other comprehensive income relating to interest in equity accounted affiliates. 18. Additional disclosures in respect of guaranteed securities (continued) Summary statements of comprehensive income for the six months ended 30 September 2017: Parent guarantor Issuer of Shares National Grid plc Niagra Mohawk Power Corporation Other subsidiaries Consolidation adjustments National Grid consolidated £m £m £m £m £m Continuing operations Revenue — 1,153 5,531 — 6,684 Operating costs — (870 ) (4,540 ) — (5,410 ) Total operating profit — 283 991 — 1,274 Net finance income/(costs) 81 (52 ) (543 ) — (514 ) Dividends receivable 150 — — (150 ) — Interest in equity accounted affiliates 461 — 5 (446 ) 20 Profit before tax 692 231 453 (596 ) 780 Tax (15 ) (87 ) (51 ) — (153 ) Profit after tax from continuing operations 677 144 402 (596 ) 627 Profit after tax from discontinued operations — — 50 — 50 Profit for the year 677 144 452 (596 ) 677 Amounts recognised in other comprehensive income from continuing operations 1 255 — 517 (517 ) 255 Amounts recognised in other comprehensive income from discontinued operations 1 64 — — — 64 Total comprehensive income for the year 996 144 969 (1,113 ) 996 Attributable to: Equity shareholders 996 144 969 (1,113 ) 996 Non-controlling interests — — — — — 996 144 969 (1,113 ) 996 1. Includes other comprehensive income relating to interest in equity accounted affiliates.
Schedule of Condensed Balance Sheet	Summary statements of financial position as at 30 September 2018: Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Non-current assets Goodwill — 743 5,117 — 5,860 Other intangible assets — 3 987 — 990 Property, plant and equipment — 6,769 35,892 — 42,661 Other non-current assets 9 6 90 (9 ) 96 Amounts owed by subsidiary undertakings 352 — 2,109 (2,461 ) — Pension assets — 268 1,486 — 1,754 Financial and other investments 22,983 34 3,779 (25,513 ) 1,283 Derivative financial assets 8 6 1,145 — 1,159 Total non-current assets 23,352 7,829 50,605 (27,983 ) 53,803 Current assets Inventories and current intangible assets — 61 379 — 440 Trade and other receivables — 574 1,761 — 2,335 Current tax assets — — 298 (209 ) 89 Amounts owed by subsidiary undertakings 12,710 84 13,949 (26,743 ) — Financial and other investments 718 2 938 — 1,658 Derivative financial assets 546 11 99 (467 ) 189 Cash and cash equivalents 67 3 60 — 130 Assets held for sale — — 2,121 — 2,121 Total current assets 14,041 735 19,605 (27,419 ) 6,962 Total assets 37,393 8,564 70,210 (55,402 ) 60,765 Current liabilities Borrowings (832 ) (625 ) (2,677 ) — (4,134 ) Derivative financial liabilities (58 ) (6 ) (758 ) 467 (355 ) Trade and other payables (64 ) (323 ) (2,757 ) — (3,144 ) Contract liabilities — — (26 ) — (26 ) Amounts owed to subsidiary undertakings (14,000 ) (36 ) (12,707 ) 26,743 — Current tax liabilities — (217 ) (129 ) 209 (137 ) Provisions — (20 ) (359 ) — (379 ) Liabilities held for sale — — (50 ) — (50 ) Total current liabilities (14,954 ) (1,227 ) (19,463 ) 27,419 (8,225 ) Non-current liabilities Borrowings (782 ) (1,667 ) (21,061 ) — (23,510 ) Derivative financial liabilities (232 ) (6 ) (542 ) — (780 ) Other non-current liabilities — (472 ) (396 ) — (868 ) Contract liabilities — — (834 ) — (834 ) Amounts owed to subsidiary undertakings (2,108 ) — (353 ) 2,461 — Deferred tax liabilities — (694 ) (3,217 ) 9 (3,902 ) Pensions and other post-retirement benefit obligations — (757 ) (667 ) — (1,424 ) Provisions — (280 ) (1,607 ) — (1,887 ) Total non-current liabilities (3,122 ) (3,876 ) (28,677 ) 2,470 (33,205 ) Total liabilities (18,076 ) (5,103 ) (48,140 ) 29,889 (41,430 ) Net assets 19,317 3,461 22,070 (25,513 ) 19,335 Equity Share capital 457 144 180 (324 ) 457 Share premium account 1,316 2,362 9,032 (11,394 ) 1,316 Retained earnings 21,587 954 12,732 (13,686 ) 21,587 Other equity reserves (4,043 ) 1 108 (109 ) (4,043 ) Shareholders’ equity 19,317 3,461 22,052 (25,513 ) 19,317 Non-controlling interests — — 18 — 18 Total equity 19,317 3,461 22,070 (25,513 ) 19,335 18. Additional disclosures in respect of guaranteed securities (continued) Summary statements of financial position as at 31 March 2018: Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Non-current assets Goodwill — 691 4,753 — 5,444 Other intangible assets — 3 896 — 899 Property, plant and equipment — 6,148 33,705 — 39,853 Other non-current assets — 3 112 — 115 Amounts owed by subsidiary undertakings 350 — 2,092 (2,442 ) — Pension assets — 231 1,178 — 1,409 Financial and other investments 21,708 30 5,221 (23,892 ) 3,067 Derivative financial assets 18 2 1,299 — 1,319 Total non-current assets 22,076 7,108 49,256 (26,334 ) 52,106 Current assets Inventories and current intangible assets — 36 305 — 341 Trade and other receivables — 515 2,283 — 2,798 Current tax assets — — 307 (193 ) 114 Amounts owed by subsidiary undertakings 11,253 130 11,777 (23,160 ) — Financial and other investments 939 15 1,740 — 2,694 Derivative financial assets 308 7 46 44 405 Cash and cash equivalents — 4 325 — 329 Total current assets 12,500 707 16,783 (23,309 ) 6,681 Total assets 34,576 7,815 66,039 (49,643 ) 58,787 Current liabilities Borrowings (779 ) (51 ) (3,617 ) — (4,447 ) Derivative financial liabilities (187 ) (36 ) (134 ) (44 ) (401 ) Trade and other payables (62 ) (318 ) (3,073 ) — (3,453 ) Amounts owed to subsidiary undertakings (11,810 ) — (11,350 ) 23,160 — Current tax liabilities — (202 ) (114 ) 193 (123 ) Provisions — (23 ) (250 ) — (273 ) Total current liabilities (12,838 ) (630 ) (18,538 ) 23,309 (8,697 ) Non-current liabilities Borrowings (773 ) (2,087 ) (19,318 ) — (22,178 ) Derivative financial liabilities (41 ) (18 ) (601 ) — (660 ) Other non-current liabilities — (281 ) (1,036 ) — (1,317 ) Amounts owed to subsidiary undertakings (2,092 ) — (350 ) 2,442 — Deferred tax liabilities — (626 ) (3,010 ) — (3,636 ) Pensions and other post-retirement benefit obligations — (765 ) (907 ) — (1,672 ) Provisions — (248 ) (1,531 ) — (1,779 ) Total non-current liabilities (2,906 ) (4,025 ) (26,753 ) 2,442 (31,242 ) Total liabilities (15,744 ) (4,655 ) (45,291 ) 25,751 (39,939 ) Net assets 18,832 3,160 20,748 (23,892 ) 18,848 Equity Share capital 452 133 180 (313 ) 452 Share premium account 1,321 2,194 9,032 (11,226 ) 1,321 Retained earnings 21,599 830 11,511 (12,341 ) 21,599 Other equity reserves (4,540 ) 3 9 (12 ) (4,540 ) Shareholders’ equity 18,832 3,160 20,732 (23,892 ) 18,832 Non-controlling interests — — 16 — 16 Total equity 18,832 3,160 20,748 (23,892 ) 18,848
Schedule of Condensed Cash Flow Statement	Summary cash flow statements for the six month periods ended 30 September 2018 and 30 September 2017 : Parent Issuer of shares National Niagra Mohawk Power Corporation Other Consolidation National £m £m £m £m £m Period ended 30 September 2018 Net cash flow from operating activities – continuing operations 2 236 1,697 — 1,935 Net cash flow used in operating activities – discontinued operations — — (47 ) — (47 ) Net cash flow (used in)/from investing activities – continuing operations (265 ) (171 ) (545 ) 193 (788 ) Net cash flow from investing activities – discontinued operations — — 78 — 78 Net cash flow from/(used in) financing activities – continuing operations 330 (65 ) (1,452 ) (193 ) (1,380 ) Net cash flow from financing activities – discontinued operations — — — — — Net increase/(decrease) in cash and cash equivalents in the period 67 — (269 ) — (202 ) Period ended 30 September 2017 Net cash flow from operating activities – continuing operations 24 328 1,716 — 2,068 Net cash flow used in operating activities – discontinued operations — — (126 ) — (126 ) Net cash flow from/(used in) investing activities – continuing operations 3,193 155 596 280 4,224 Net cash flow from investing activities – discontinued operations — — 15 — 15 Net cash flow (used in)/from financing activities – continuing operations (4,303 ) (482 ) (1,984 ) (280 ) (7,049 ) Net cash flow used in financing activities – discontinued operations — — (231 ) — (231 ) Net (decrease)/increase in cash and cash equivalents in the period (1,086 ) 1 (14 ) — (1,099 )

Basis of preparation and new _3

Basis of preparation and new accounting standards, interpretations and amendments Areas of judgement and key sources of estimation uncertainty (Details) - 6 months ended Sep. 30, 2018 - Exceptional items [Member] £ in Millions, $ in Millions	GBP (£)	USD ($)
Disclosure of other provisions [line items]
Employee benefits expense	£ 97	$ 127
Expense of restructuring activities	127
Proceeds from legal settlements	£ 94

Segmental analysis Revenue (Det

Segmental analysis Revenue (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of operating segments [line items]
Revenue	£ 6,347	£ 6,684	[1]
UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
Revenue	1,562
UK Gas Transmission [Member]
Disclosure of operating segments [line items]
Revenue	347
US Regulated [Member]
Disclosure of operating segments [line items]
Revenue	4,053
NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Revenue	385
Operating segments [member] | UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
Revenue including inter-segment revenue	1,574	2,076
Revenue	1,562
Operating segments [member] | UK Gas Transmission [Member]
Disclosure of operating segments [line items]
Revenue including inter-segment revenue	353	422
Revenue	347
Operating segments [member] | US Regulated [Member]
Disclosure of operating segments [line items]
Revenue including inter-segment revenue	4,053	3,799
Revenue	4,053
Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Revenue including inter-segment revenue	387	407
Revenue	385
Unallocated amounts [member] | NG Ventures [Member]
Disclosure of operating segments [line items]
Revenue	294	294
Unallocated amounts [member] | UK Property Development [Member]
Disclosure of operating segments [line items]
Revenue	44	59
Elimination of intersegment amounts [member]
Disclosure of operating segments [line items]
Revenue including inter-segment revenue	(20)	(20)
Country of domicile [member]
Disclosure of operating segments [line items]
Revenue	2,272	2,865
Foreign countries [member]
Disclosure of operating segments [line items]
Revenue	£ 4,075	£ 3,819
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Segmental analysis Operating pr

Segmental analysis Operating profit - Segment components (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ 1,017	£ 1,274	[1],[2]
Before exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,202	1,259	[1]
Before exceptional items and remeasurements [Member] | Operating segments [member] | UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	531	542
Before exceptional items and remeasurements [Member] | Operating segments [member] | UK Gas Transmission [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	79	126
Before exceptional items and remeasurements [Member] | Operating segments [member] | US Regulated [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	385	433
Before exceptional items and remeasurements [Member] | Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	207	158
After exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,017	1,274
After exceptional items and remeasurements [Member] | Operating segments [member] | UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	437	542
After exceptional items and remeasurements [Member] | Operating segments [member] | UK Gas Transmission [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	46	126
After exceptional items and remeasurements [Member] | Operating segments [member] | US Regulated [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	327	448
After exceptional items and remeasurements [Member] | Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	207	158
Exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	(185)	15	[1]
Exceptional items and remeasurements [Member] | UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
Other operating income (expense)	(94)	0
Exceptional items and remeasurements [Member] | UK Gas Transmission [Member]
Disclosure of operating segments [line items]
Other operating income (expense)	(33)	0
Exceptional items and remeasurements [Member] | US Regulated [Member]
Disclosure of operating segments [line items]
Other operating income (expense)	(58)	(15)
Country of domicile [member] | Before exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	761	852
Country of domicile [member] | After exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	634	852
Foreign countries [member] | Before exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	441	407
Foreign countries [member] | After exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ 383	£ 422
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Segmental analysis Operating _2

Segmental analysis Operating profit - Reconciliation (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ 1,017	£ 1,274	[1],[2]
Share of post-tax results of joint ventures and associates	25	20	[1]
Finance income	42	24	[1]
Finance costs	(562)	(538)	[1]
Profit/(loss) before tax	522	780	[1]
NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Proceeds from legal settlements	94	0
Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Share of post-tax results of joint ventures and associates	131	132
Unallocated amounts [member] | UK Property Development [Member]
Disclosure of operating segments [line items]
Share of post-tax results of joint ventures and associates	38	53
Before exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,202	1,259	[1]
Share of post-tax results of joint ventures and associates	25	20	[1]
Finance income	42	24	[1]
Finance costs	(536)	(566)	[1]
Profit/(loss) before tax	733	737	[1]
Before exceptional items and remeasurements [Member] | Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	207	158
Share of post-tax results of joint ventures and associates	25	20
After exceptional items and remeasurements [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,017	1,274
Finance income	42	24
Finance costs	(562)	(538)
Profit/(loss) before tax	522	780
After exceptional items and remeasurements [Member] | Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
Operating profit from continuing operations	207	158
Share of post-tax results of joint ventures and associates	£ 25	£ 20
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Segmental analysis Capital expe

Segmental analysis Capital expenditure (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Mar. 31, 2017
Disclosure of operating segments [line items]
PPE and other intangible assets, net	£ 43,651		£ 40,752
Additions to PPE and non-current intangible assets	2,040	£ 1,892
Depreciation and amortisation expense	791	762
Operating segments [member] | UK Electricity Transmission [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	13,247		13,028
Additions to PPE and non-current intangible assets	462	515
Depreciation and amortisation expense	242	226
Operating segments [member] | UK Gas Transmission [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	4,345		4,280
Additions to PPE and non-current intangible assets	153	157
Depreciation and amortisation expense	92	94
Operating segments [member] | US Regulated [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	23,395		20,953
Additions to PPE and non-current intangible assets	1,177	1,095
Depreciation and amortisation expense	346	328
Unallocated amounts [member] | NG Ventures And Other [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	2,664		2,491
Additions to PPE and non-current intangible assets	248	125
Depreciation and amortisation expense	111	114
Unallocated amounts [member] | NG Ventures [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	1,518		1,454
Additions to PPE and non-current intangible assets	136	72
Depreciation and amortisation expense	64	68
Unallocated amounts [member] | UK Property Development [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	60			£ 52
Additions to PPE and non-current intangible assets	11	5
Depreciation and amortisation expense	1	0
Country of domicile [member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	19,094		18,772
Additions to PPE and non-current intangible assets	782	751
Depreciation and amortisation expense	399	393
Foreign countries [member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	24,557		21,980
Additions to PPE and non-current intangible assets	1,258	1,141
Depreciation and amortisation expense	392	369
Property, plant and equipment [member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	42,661		39,853
Additions to PPE and non-current intangible assets	1,900	1,820
Depreciation and amortisation expense	710	689
Intangible Assets [Member]
Disclosure of operating segments [line items]
PPE and other intangible assets, net	990		£ 899
Additions to PPE and non-current intangible assets	140	72
Depreciation and amortisation expense	£ 81	£ 73

Revenue (Details)

Revenue (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	£ 5,964
Other revenue	383
Revenue	6,347	£ 6,684	[1]
UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	1,559
Other revenue	3
Revenue	1,562
UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	322
Other revenue	25
Revenue	347
US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,793
Other revenue	260
Revenue	4,053
NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	290
Other revenue	95
Revenue	385
Country of domicile [member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	2,171
Other revenue	101
Revenue	2,272	2,865
Country of domicile [member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	1,559
Other revenue	3
Country of domicile [member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	322
Other revenue	25
Country of domicile [member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	0
Country of domicile [member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	290
Other revenue	73
Foreign countries [member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,793
Other revenue	282
Revenue	4,075	£ 3,819
Foreign countries [member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	0
Foreign countries [member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	0
Foreign countries [member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,793
Other revenue	260
Foreign countries [member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	22
Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	2,348
Distribution [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,478
Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	138
Other revenue	200
Generation [Member]
Revenue from Contracts with Customers [line items]
Other revenue	183
Operating segments [member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	1,559
Other revenue	3
Revenue	1,562
Operating segments [member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	322
Other revenue	25
Revenue	347
Operating segments [member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,793
Other revenue	260
Revenue	4,053
Operating segments [member] | Transmission [Member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	1,559
Operating segments [member] | Transmission [Member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	322
Operating segments [member] | Transmission [Member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	315
Operating segments [member] | Distribution [Member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Operating segments [member] | Distribution [Member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Operating segments [member] | Distribution [Member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	3,478
Operating segments [member] | Other [Member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	3
Operating segments [member] | Other [Member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	25
Operating segments [member] | Other [Member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Other revenue	77
Operating segments [member] | Generation [Member] | UK Electricity Transmission [Member]
Revenue from Contracts with Customers [line items]
Other revenue	0
Operating segments [member] | Generation [Member] | UK Gas Transmission [Member]
Revenue from Contracts with Customers [line items]
Other revenue	0
Operating segments [member] | Generation [Member] | US Regulated [Member]
Revenue from Contracts with Customers [line items]
Other revenue	183
Unallocated amounts [member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	290
Other revenue	95
Revenue	385
Unallocated amounts [member] | Transmission [Member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	152
Unallocated amounts [member] | Distribution [Member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	0
Unallocated amounts [member] | Other [Member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Revenue under IFRS 15	138
Other revenue	95
Unallocated amounts [member] | Generation [Member] | NG Ventures And Other [Member]
Revenue from Contracts with Customers [line items]
Other revenue	£ 0
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Exceptional items and remeasu_3

Exceptional items and remeasurements (Details) £ in Millions, $ in Millions	6 Months Ended
	Sep. 30, 2018GBP (£)	Sep. 30, 2018USD ($)	Sep. 30, 2017GBP (£)
Included within operating profit [Abstract]
Operating costs	£ (5,330)		£ (5,410)	[1]
Included within net finance costs [Abstract]
Finance costs	(562)		(538)	[1]
Profit/(loss) before tax	522		780	[1]
Tax	(93)		(153)	[1]
Profit after tax from continuing operations	429		627	[1],[2]
Restructuring provision	100
Payments for restructuring	18
Exceptional items [Member]
Included within operating profit [Abstract]
Expense of restructuring activities	127
Employee benefits expense	(97)	$ (127)
Gains (losses) on derivatives financial instruments, operating	0		0
Operating costs	(224)		0
Included within net finance costs [Abstract]
Gains (losses) on financial assets at fair value through profit or loss	0
Gains (losses) on financial liabilities at fair value through profit or loss	0
Finance costs	0
Profit/(loss) before tax	(224)		0
Tax	48		0
Profit after tax from continuing operations	(176)		0
Cash outflow for workforce contingency plan	102	$ 134
Remeasurements [Member]
Included within operating profit [Abstract]
Expense of restructuring activities	0
Employee benefits expense
Gains (losses) on derivatives financial instruments, operating	(26)		28
Operating costs	39		15
Included within net finance costs [Abstract]
Gains (losses) on financial assets at fair value through profit or loss	8
Gains (losses) on financial liabilities at fair value through profit or loss	(8)
Finance costs	(26)		28
Profit/(loss) before tax	13		43
Tax	(7)		(4)
Profit after tax from continuing operations	6		39
Exceptional items and remeasurements [Member]
Included within operating profit [Abstract]
Expense of restructuring activities	127
Employee benefits expense	(97)
Gains (losses) on derivatives financial instruments, operating	(26)		28
Operating costs	(185)		15	[1]
Included within net finance costs [Abstract]
Gains (losses) on financial assets at fair value through profit or loss	8
Gains (losses) on financial liabilities at fair value through profit or loss	(8)
Finance costs	(26)		28	[1]
Profit/(loss) before tax	(211)		43	[1]
Tax	41		(4)	[1]
Profit after tax from continuing operations	(170)		39	[1]
Commodity Derivatives [Member] | Exceptional items [Member]
Included within operating profit [Abstract]
Gains (losses) on derivatives financial instruments, operating	0		0
Commodity Derivatives [Member] | Remeasurements [Member]
Included within operating profit [Abstract]
Gains (losses) on derivatives financial instruments, operating	39		15
Commodity Derivatives [Member] | Exceptional items and remeasurements [Member]
Included within operating profit [Abstract]
Gains (losses) on derivatives financial instruments, operating	£ 39		£ 15
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Finance income and costs (Detai

Finance income and costs (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Finance income before exceptional items and remeasurements [Abstract]
Finance income	£ 42	£ 24	[1]
Finance costs before exceptional items and remeasurements [abstract]
Finance costs	562	538	[1]
Net finance costs [Abstract]
Finance income (cost)	(520)	(514)
Before exceptional items and remeasurements [Member]
Finance income before exceptional items and remeasurements [Abstract]
Finance income	42	24	[1]
Finance costs before exceptional items and remeasurements [abstract]
Net interest on defined benefit plan	(11)	(33)
Interest expense on debt instruments issued	(555)	(546)
Expense due to unwinding of discount on provisions	(35)	(38)
Interest expense on other financial liabilities	(9)	(8)
Interest costs capitalised	74	59
Finance costs	536	566	[1]
Net finance costs [Abstract]
Finance income (cost)	(494)	(542)
Exceptional items and remeasurements [Member]
Finance income before exceptional items and remeasurements [Abstract]
Finance income	0	0	[1]
Finance costs before exceptional items and remeasurements [abstract]
Finance costs	26	(28)	[1]
Net finance costs [Abstract]
Finance income (cost)	(26)	28
Quadgas HoldCo Limited [Member] | Discontinued operations [member]
Net finance costs [Abstract]
Interest received from associates	£ 12	£ 15
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Held for sale and discontinue_2

Held for sale and discontinued operations – Interests in Quadgas HoldCo Limited (Details) - GBP (£)	May 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017		Mar. 31, 2018	Mar. 31, 2017
Disclosure of associates [line items]
Purchase of interests in investments accounted for using equity method				£ 84,000,000	£ 77,000,000	[1]
Derivative financial liabilities				1,135,000,000			£ 1,061,000,000
Derivative financial assets				1,348,000,000			£ 1,724,000,000
Tax expense relating to profit (loss) from ordinary activities of discontinued operations				2,000,000	3,000,000
Remeasurement gains on pension assets and post-retirement benefit obligations				606,000,000	594,000,000	[2]
Net gains/(losses) in respect of hedging arrangements				(31,000,000)	16,000,000	[2]
Quadgas Holdco Limited Cadent [Member]
Disclosure of associates [line items]
Proportion of ownership interest disposed								61.00%
Proportion of ownership interest in associate								39.00%
Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans				£ 35,000,000	60,000,000
Quadgas HoldCo Limited [Member]
Disclosure of associates [line items]
Proportion of ownership interest in associate				39.00%
Proportion of ownership interest in associate, put/call option equity interest				14.00%				14.00%
Proportion of ownership interest in associate, excluding put/call option equity interest	25.00%						25.00%
Purchase of interests in investments accounted for using equity method				£ 2,100,000,000			£ 2,100,000,000
Receivables due from associates				400,000,000
Investments in associates				1,600,000,000
Share of post-tax profit (loss) from discontinued operations of associates and joint ventures accounted for using equity method		£ 38,000,000	£ 52,000,000
Put/Call Option Derivatives - RAA [Member]
Disclosure of associates [line items]
Derivative financial liabilities				43,000,000			0
Put/Call Option Derivatives - FAA [Member]
Disclosure of associates [line items]
Derivative financial assets				87,000,000			£ 110,000,000
Discontinued operations [member]
Disclosure of associates [line items]
Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans		2,000,000	0
Remeasurement gains on pension assets and post-retirement benefit obligations		35,000,000	60,000,000
Net gains/(losses) in respect of hedging arrangements		£ 1,000,000	£ 4,000,000
Discontinued operations [member] | Quadgas HoldCo Limited [Member]
Disclosure of associates [line items]
Impairment loss on investments accounted for as equity method investments				43,000,000
Interest income on loans and receivables				12,000,000	15,000,000
Dividends received				66,000,000	0
Interest received from associates				£ 12,000,000	£ 15,000,000
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Tax from continuing operations

Tax from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended			12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Mar. 31, 2019	Mar. 31, 2018
Disclosure of Income Taxes [Line Items]
Tax expense (income), continuing operations	£ 93	£ 153	[1]
Average effective tax rate				20.00%	(33.40%)
Before exceptional items and remeasurements [Member]
Disclosure of Income Taxes [Line Items]
Tax expense (income), continuing operations	£ 134	£ 149	[1]
Average effective tax rate	18.30%	20.20%			23.40%
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Earnings per share (Details)

Earnings per share (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity		£ 428	£ 626
Basic earnings per share (continuing) (in GBP per share)		£ 0.127	£ 0.177	[1]
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity		£ 3	£ 50
Basic earnings (loss) per share (discontinued) (in GBP per share)		£ 0.001	£ 0.014
Profit (loss), attributable to ordinary equity holders of parent entity		£ 431	£ 676
Basic earnings per share (continuing and discontinued) (in GBP per share)		£ 0.128	£ 0.191	[1]
Weighted average number of ordinary shares outstanding (in shares)		3,367	3,539
Diluted earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity including dilutive effects		£ 428	£ 626
Diluted earnings per share (continuing) (in GBP per share)		£ 0.126	£ 0.176	[1]
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity including dilutive effects		£ 3	£ 50
Diluted earnings (loss) per share (discontinued) (GBP per share)		£ 0.001	£ 0.014
Profit (loss), attributable to ordinary equity holders of parent entity including dilutive effects		£ 431	£ 676
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ 0.127	£ 0.190	[1]
Adjusted weighted average number of ordinary shares outstanding (in shares)		3,381	3,554
Before exceptional items and remeasurements [Member]
Basic earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity		£ 598	£ 587
Basic earnings per share (continuing) (in GBP per share)		£ 0.178	£ 0.166
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity		£ 48	£ 67
Basic earnings (loss) per share (discontinued) (in GBP per share)		£ 0.014	£ 0.019
Profit (loss), attributable to ordinary equity holders of parent entity		£ 646	£ 654
Basic earnings per share (continuing and discontinued) (in GBP per share)		£ 0.192	£ 0.185
Diluted earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity including dilutive effects		£ 598	£ 587
Diluted earnings per share (continuing) (in GBP per share)		£ 0.177	£ 0.165
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity including dilutive effects		£ 48	£ 67
Diluted earnings (loss) per share (discontinued) (GBP per share)		£ 0.014	£ 0.019
Profit (loss), attributable to ordinary equity holders of parent entity including dilutive effects		£ 646	£ 654
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ 0.191	£ 0.184
Exceptional items and remeasurements [Member]
Basic earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity		£ (170)	£ 39
Basic earnings per share (continuing) (in GBP per share)		£ (0.051)	£ 0.011
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity		£ (45)	£ (17)
Basic earnings (loss) per share (discontinued) (in GBP per share)		£ (0.013)	£ (0.005)
Profit (loss), attributable to ordinary equity holders of parent entity		£ (215)	£ 22
Basic earnings per share (continuing and discontinued) (in GBP per share)		£ (0.064)	£ 0.006
Diluted earnings per share [abstract]
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity including dilutive effects		£ (170)	£ 39
Diluted earnings per share (continuing) (in GBP per share)		£ (0.051)	£ 0.011
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity including dilutive effects		£ (45)	£ (17)
Diluted earnings (loss) per share (discontinued) (GBP per share)		£ (0.013)	£ (0.005)
Profit (loss), attributable to ordinary equity holders of parent entity including dilutive effects		£ (215)	£ 22
Diluted earnings per share (continuing and discontinued) (in GBP per share)		£ (0.064)	£ 0.006
Special Dividend [Member]
Diluted earnings per share [abstract]
Dividends paid, ordinary shares	£ 3,171
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Dividends (Details)

Dividends (Details) - GBP (£) £ / shares in Units, £ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Final Dividend in Respect of Prior Year [Member]
Summary Of Dividends [Line Items]
Dividends paid, ordinary shares per share (GBP per share)			£ 0.3044
Dividends paid, ordinary shares			£ 710
Scrip dividends related share issue recognized			£ 319
Special Dividend [Member]
Summary Of Dividends [Line Items]
Dividends paid, ordinary shares per share (GBP per share)	£ 0.84375
Dividends paid, ordinary shares	£ 3,171
Scrip dividends related share issue recognized	£ 0
Final Dividend in Respect of 2 Years Ago [Member]
Summary Of Dividends [Line Items]
Dividends paid, ordinary shares per share (GBP per share)				£ 0.2910
Dividends paid, ordinary shares				£ 970
Scrip dividends related share issue recognized				£ 33
Interim Dividend in Respect of Current Year [Member]
Summary Of Dividends [Line Items]
Dividends paid, ordinary shares per share (GBP per share)		£ 0.1608
Dividends paid, ordinary shares		£ 547
Interim Dividend in Respect of Prior Year [Member]
Summary Of Dividends [Line Items]
Dividends paid, ordinary shares per share (GBP per share)			£ 0.1549
Dividends paid, ordinary shares			£ 346
Scrip dividends related share issue recognized			£ 176

Fair value measurement Assets a

Fair value measurement Assets and liabilities measured at fair value (Details) - GBP (£) £ in Millions	May 01, 2018	Sep. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		£ 60,765	£ 58,787
Liabilities		(41,430)	(39,939)
Net assets		19,335	18,848
Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		3,100	4,524
Liabilities		(1,780)	(1,061)
Net assets		1,320	3,463
Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,302	2,406
Liabilities		(645)	0
Net assets		657	2,406
Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,602	1,862
Liabilities		(861)	(779)
Net assets		741	1,083
Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		196	256
Liabilities		(274)	(282)
Net assets		(78)	(26)
Derivatives [member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(1,022)	(945)
Derivatives [member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		0	0
Derivatives [member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(828)	(725)
Derivatives [member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(194)	(220)
Commodity Derivatives [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(113)	(116)
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		0	0
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(33)	(54)
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(80)	(62)
Liabilities Held at Fair Value [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(645)	0
Liabilities Held at Fair Value [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		(645)	0
Liabilities Held at Fair Value [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		0	0
Liabilities Held at Fair Value [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities		0	0
Available-for-Sale Investments [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	2,721
Available-for-Sale Investments [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	2,406
Available-for-Sale Investments [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	310
Available-for-Sale Investments [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	5
Investments held at FVTPL [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,219	0
Investments held at FVTPL [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,194	0
Investments held at FVTPL [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Investments held at FVTPL [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		25	0
Investments held at FVTOCI [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		446	0
Investments held at FVTOCI [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		108	0
Investments held at FVTOCI [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		338	0
Investments held at FVTOCI [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Associates [member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		87	79
Associates [member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Associates [member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Associates [member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		87	79
Derivatives [member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,247	1,545
Derivatives [member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Derivatives [member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1,246	1,544
Derivatives [member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		1	1
Commodity Derivatives [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		101	69
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		18	8
Commodity Derivatives [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		83	61
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	110
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 1 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 2 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		0	0
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets		£ 0	£ 110
Quadgas HoldCo Limited [Member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Proportion of ownership interest in associate, put/call option equity interest		14.00%		14.00%
Proportion of ownership interest in associate, excluding put/call option equity interest	25.00%		25.00%
Quadgas HoldCo Limited [Member] | Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets			£ 110

Fair value measurement Narrativ

Fair value measurement Narrative (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings	£ 27,644	£ 26,625
Minimum deviation of growth curve to be considered observable for fair value measurement	5.00%
At fair value [member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings	£ 30,466	£ 30,164
Interest Rate Risk, Fifty Basis Point Increase In Discount Rate [Member] | Sunrun Neptune 2016 LLC [Member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Risk exposure associated with instruments sharing characteristic	(4)		£ (4)
Interest Rate Risk, Fifty Basis Point Decrease In Discount Rate [Member] | Sunrun Neptune 2016 LLC [Member]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Risk exposure associated with instruments sharing characteristic	£ 4		£ 4

Fair value measurement Assumpti

Fair value measurement Assumptions used in valuing assets and liabilities (Details) - GBP (£) £ in Millions	Mar. 31, 2018	Mar. 31, 2017
Commodity Derivatives [Member] | Commodity Price Risk, Ten Percent Increase [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis 10% increase in commodity prices	£ 1	£ (2)
Commodity Derivatives [Member] | Commodity Price Risk, Ten Percent Decrease [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis 10% decrease in commodity prices	(2)	2
Commodity Derivatives [Member] | Market Risk, Market Area Price Ten Percent Increase [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis 10% increase in area price change	(8)	(7)
Commodity Derivatives [Member] | Market Risk, Market Area Price Ten Percent Decrease [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis 10% decrease in area price change	7	5
Financing Derivatives [Member] | Market Risk, Limited Price Inflation Market Curve Twenty Basis Points Increase [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis 20 basis point change increase market curve	(81)	(85)
Financing Derivatives [Member] | Market Risk, Limited Price Inflation Market Curve Twenty Basis Points Decrease [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity analysis, 20 basis point change decrease in market curve	£ 79	£ 82

Fair value measurement Movement

Fair value measurement Movements in assets and liabilities (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets	£ 60,765		£ 58,787
Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Transfers into Level 3 of fair value hierarchy, assets (liabilities)		£ 0
Financing and Put/Call Option Derivatives [Member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(219)	(465)
Net gains/(losses) through the income statement for the period	26	8
Net gains through other comprehensive income for the period	0	0
Transfer to held for sale	0	0
Purchases	0	0
Settlements	0	231
Financial assets (liabilities), ending balance	(193)	(226)
Gains (losses) recognized in P&L, fair value measurement, assets (liabilities) held at end of period	26	5
Commodity Derivatives [Member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(1)	(16)
Net gains/(losses) through the income statement for the period	(16)	(1)
Net gains through other comprehensive income for the period	0	0
Transfer to held for sale	0	0
Purchases	6	0
Settlements	13	26
Financial assets (liabilities), ending balance	2	9
Gains (losses) recognized in P&L, fair value measurement, assets (liabilities) held at end of period	11	1
Investments held at FVTPL [Member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	194	46
Net gains/(losses) through the income statement for the period	4	(2)
Net gains through other comprehensive income for the period	6	0
Transfer to held for sale	(110)	0
Purchases	21	35
Settlements	(2)	0
Financial assets (liabilities), ending balance	113	£ 79
Recurring fair value measurement [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets	3,100		4,524
Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets	196		256
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets	0		110
Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets	£ 0		110
Quadgas HoldCo Limited [Member] | Put/Call Option Derivatives - FAA [Member] | Recurring fair value measurement [member] | Level 3 of fair value hierarchy [member]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Assets			£ 110

Net debt (Details)

Net debt (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Mar. 31, 2017
Disclosure of detailed information about financial instruments [line items]
Cash, cash equivalents and current financial investments	£ 1,788		£ 3,023
Borrowings and bank overdrafts	(27,644)		(26,625)
Financing derivatives	213		663
Net debt (net of related derivative financial instruments)	25,631	£ 23,075	23,002	£ 19,274
Financing derivatives relating to purchase of PPE, classified as investing activities	76	£ 67
Derivatives [member]
Disclosure of detailed information about financial instruments [line items]
Financing derivatives	£ 225		£ 600

Net debt Derivatives on Balance

Net debt Derivatives on Balance Sheet (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	£ 1,348	£ 1,724
Derivative financial liabilities	(1,135)	(1,061)
Financing derivatives	213	663
Derivatives [member]
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	1,247	1,545
Derivative financial liabilities	(1,022)	(945)
Financing derivatives	225	600
Commodity Derivatives [Member]
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	101	69
Derivative financial liabilities	(113)	(116)
Financing derivatives	(12)	(47)
Put/Call Option Derivatives - FAA [Member]
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	£ 87	110
Financing derivatives		£ 110

Analysis of changes in net de_3

Analysis of changes in net debt (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Increase (Decrease) In Cash And Cash Equivalents [Roll Forward]
Cash and cash equivalents	£ 329	£ 1,139
Increase (decrease) in cash and cash equivalents, excluding bank overdrafts	(202)	(1,099)
Effect of exchange rate changes on cash and cash equivalents excluding bank overdrafts	3	(1)
Cash and cash equivalents	130	39
Increase (Decrease) In Financial Investments [Roll Forward]
Financial and other investments	2,694	8,741
Increase (decrease) in financial investments	(1,171)	(6,148)
Effect of exchange rate changes and fair value gains and losses on financial investments	95	(40)
Increase (decrease) in financial investments, interest income	16	20
Other non-cash movements on financial investments	24
Financial and other investments	1,658	2,573
Increase (Decrease) In Borrowings [Roll Forward]
Borrowings, excluding bank overdrafts		(28,638)
Increase (decrease) in borrowings	424	2,592
Effect of exchange rate changes and fair value gains and losses on borrowings	(851)	522
Increase (decrease) in borrowings, interest expense	(540)	(546)
Increase (decrease) in borrowings, other non-cash movements	(20)	(39)
Borrowings, excluding bank overdrafts	(27,644)	(26,109)
Increase (Decrease) In Financing Derivatives [Roll Forward]
Financing derivatives		(516)
Increase (decrease) in financing derivatives	260	144
Effect of exchange rate changes and fair value gains and losses on financing derivatives	(620)	789
Increase (decrease) in financing derivatives, interest income (expense)	(15)	5
Financing derivatives	225	422
Increase (Decrease) In Net Debt [Roll Forward]
Net debt	(23,002)	(19,274)
Change in net debt from cash flows	(689)	(4,511)
Effect of exchange rate changes and fair value gains and losses on net debt	(1,373)	1,270
Increase (decrease) in net debt, net interest expense	(539)	(521)
Increase (decrease) in net debt, other non-cash movements	4	(39)
Net debt	(25,631)	(23,075)
Interest received in relation to litigation settlement	17	0
Previously stated [member]
Increase (Decrease) In Cash And Cash Equivalents [Roll Forward]
Cash and cash equivalents	329
Increase (Decrease) In Financial Investments [Roll Forward]
Financial and other investments	2,694
Increase (Decrease) In Borrowings [Roll Forward]
Borrowings, excluding bank overdrafts	(26,625)
Increase (Decrease) In Financing Derivatives [Roll Forward]
Financing derivatives	600
Increase (Decrease) In Net Debt [Roll Forward]
Net debt	(23,002)
Increase (decrease) due to changes in accounting policy required by IFRS 9 and IFRS 15 [Member]
Increase (Decrease) In Cash And Cash Equivalents [Roll Forward]
Cash and cash equivalents	0
Increase (Decrease) In Financial Investments [Roll Forward]
Financial and other investments	0
Increase (Decrease) In Borrowings [Roll Forward]
Borrowings, excluding bank overdrafts	(32)
Increase (Decrease) In Financing Derivatives [Roll Forward]
Financing derivatives	0
Increase (Decrease) In Net Debt [Roll Forward]
Net debt	(32)
Currently stated [member]
Increase (Decrease) In Cash And Cash Equivalents [Roll Forward]
Cash and cash equivalents	329
Increase (Decrease) In Financial Investments [Roll Forward]
Financial and other investments	2,694
Increase (Decrease) In Borrowings [Roll Forward]
Borrowings, excluding bank overdrafts	(26,657)
Increase (Decrease) In Financing Derivatives [Roll Forward]
Financing derivatives	600
Increase (Decrease) In Net Debt [Roll Forward]
Net debt	(23,034)
Exceptional items [Member]
Increase (Decrease) In Net Debt [Roll Forward]
Change in net debt from cash flows	0	(3)
Increase (decrease) in net debt, net interest expense	£ 0	£ 3

Pensions and other post-retir_3

Pensions and other post-retirement benefit obligations Defined benefit plan recognised in balance sheet (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018
Disclosure of defined benefit plans [line items]
Net defined benefit liability	£ (1,424)	£ (1,672)
Net defined benefit asset	1,754	1,409
Surplus (deficit) in plan	330	(263)
Pensions [Member] | Funded [Member]
Disclosure of defined benefit plans [line items]
Defined benefit obligation, at present value	(23,601)	(23,747)
Plan assets, at fair value	24,307	23,858
Surplus (deficit) in plan	706	111
Pensions [Member] | Unfunded [Member]
Disclosure of defined benefit plans [line items]
Defined benefit obligation, at present value	(318)	(307)
Foreign post-employment benefits [Member]
Disclosure of defined benefit plans [line items]
Other post-employment liabilities	£ (58)	£ (67)

Pensions and other post-retir_4

Pensions and other post-retirement benefit obligations Actuarial assumptions (Details)	Sep. 30, 2018	Mar. 31, 2018
Disclosure of defined benefit plans [line items]
Rate of increase in RPI - past service	3.25%	3.15%
Country of domicile [member]
Disclosure of defined benefit plans [line items]
Discount rate - UK past service	2.85%	2.60%
Foreign countries [member]
Disclosure of defined benefit plans [line items]
Discount rate - US	4.25%	4.00%

Pensions and other post-retir_5

Pensions and other post-retirement benefit obligations Narrative (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Mar. 31, 2018
Disclosure of defined benefit plans [line items]
Surplus (deficit) in plan	£ (330)	£ 263
Increase (decrease) in net surplus (deficit) in plan	593
Increase (decrease) in net defined benefit liability (asset)	703
Employer contributions	242
Country of domicile [member]
Disclosure of defined benefit plans [line items]
Increase (decrease) in net defined benefit liability (asset)	359
Gain (loss) on remeasurement, net defined benefit liability (asset)	135
Country of domicile [member] | National Grid UK Pension Scheme [Member]
Disclosure of defined benefit plans [line items]
Surplus (deficit) in plan	(1,277)	(1,105)
Country of domicile [member] | National Grid Electricity Group Of The Electricity Supply Pension Scheme [Member]
Disclosure of defined benefit plans [line items]
Surplus (deficit) in plan	(209)	(73)
Foreign countries [member]
Disclosure of defined benefit plans [line items]
Increase (decrease) in net defined benefit liability (asset)	344
Foreign countries [member] | Niagara Mohawk Power [Member]
Disclosure of defined benefit plans [line items]
Surplus (deficit) in plan	£ (268)	£ (231)

Commitments and contingencies (

Commitments and contingencies (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Sep. 30, 2017
Subclassifications of assets, liabilities and equities [abstract]
Authorised capital commitments but not contracted for	£ 1,851	£ 2,148

Exchange rates USD to GBP for_2

Exchange rates USD to GBP foreign exchange rates (Details) - $ / £	6 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Foreign exchange rates [abstract]
Closing rate applied at period end	1.30	1.34	1.40
Average rate applied for the period	1.31	1.31	1.36

Related party transactions (Det

Related party transactions (Details)	6 Months Ended
	Sep. 30, 2018
Quadgas HoldCo Limited [Member]
Disclosure of associates [line items]
Proportion of ownership interest in associate	39.00%

Transition to IFRS 9 and IFRS_3

Transition to IFRS 9 and IFRS 15 Impact of IFRS 9 and IFRS 15 (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Non-current assets
Goodwill	£ 5,860	£ 5,444
Other intangible assets	990	899
Property, plant and equipment	42,661	39,853
Other non-current assets	96	115
Pension assets	1,754	1,409
Financial and other investments	613	899
Investments in joint ventures and associates	670	2,168
Derivative financial assets	1,159	1,319
Total non-current assets	53,803	52,106
Current assets
Inventories and current intangible assets	440	341
Trade and other receivables	2,335	2,798
Current tax assets	89	114
Financial and other investments	1,658	2,694	£ 2,573	£ 8,741
Derivative financial assets	189	405
Cash and cash equivalents	130	329	39	1,139
Total current assets	6,962	6,681
Assets	60,765	58,787
Current liabilities
Borrowings	(4,134)	(4,447)
Derivative financial liabilities	(355)	(401)
Trade and other payables	(3,144)	(3,453)
Contract liabilities	(26)	0
Current tax liabilities	(137)	(123)
Provisions	(379)	(273)
Current liabilities	(8,225)	(8,697)
Non-current liabilities
Borrowings	(23,510)	(22,178)
Derivative financial liabilities	(780)	(660)
Other non-current liabilities	(868)	(1,317)
Contract liabilities	(834)	0
Deferred tax liabilities	(3,902)	(3,636)
Pensions and other post-retirement benefit obligations	(1,424)	(1,672)
Provisions	(1,887)	(1,779)
Non-current liabilities	(33,205)	(31,242)
Liabilities	(41,430)	(39,939)
Assets (liabilities)	19,335	18,848
Equity
Share capital	457	452
Share premium account	1,316	1,321
Retained earnings	21,587	21,599
Other equity reserves	(4,043)	(4,540)
Total shareholders’ equity	19,317	18,832
Non-controlling interests	18	16
Total equity	£ 19,335	18,848	£ 16,872	£ 20,384
Previously stated [member]
Non-current assets
Goodwill		5,444
Other intangible assets		899
Property, plant and equipment		39,853
Other non-current assets		115
Pension assets		1,409
Financial and other investments		899
Investments in joint ventures and associates		2,168
Derivative financial assets		1,319
Total non-current assets		52,106
Current assets
Inventories and current intangible assets		341
Trade and other receivables		2,798
Current tax assets		114
Financial and other investments		2,694
Derivative financial assets		405
Cash and cash equivalents		329
Total current assets		6,681
Assets		58,787
Current liabilities
Borrowings		(4,447)
Derivative financial liabilities		(401)
Trade and other payables		(3,453)
Contract liabilities		0
Current tax liabilities		(123)
Provisions		(273)
Current liabilities		(8,697)
Non-current liabilities
Borrowings		(22,178)
Derivative financial liabilities		(660)
Other non-current liabilities		(1,317)
Contract liabilities		0
Deferred tax liabilities		(3,636)
Pensions and other post-retirement benefit obligations		(1,672)
Provisions		(1,779)
Non-current liabilities		(31,242)
Liabilities		(39,939)
Assets (liabilities)		18,848
Equity
Share capital		452
Share premium account		1,321
Retained earnings		21,599
Other equity reserves		(4,540)
Total shareholders’ equity		18,832
Non-controlling interests		16
Total equity		18,848
Increase (decrease) due to application of IFRS 9 [Member]
Non-current assets
Goodwill		0
Other intangible assets		0
Property, plant and equipment		0
Other non-current assets		0
Pension assets		0
Financial and other investments		0
Investments in joint ventures and associates		0
Derivative financial assets		0
Total non-current assets		0
Current assets
Inventories and current intangible assets		0
Trade and other receivables		0
Current tax assets		0
Financial and other investments		0
Derivative financial assets		0
Cash and cash equivalents		0
Total current assets		0
Assets		0
Current liabilities
Borrowings		0
Derivative financial liabilities		0
Trade and other payables		0
Contract liabilities		0
Current tax liabilities		0
Provisions		0
Current liabilities		0
Non-current liabilities
Borrowings		(32)
Derivative financial liabilities		0
Other non-current liabilities		0
Contract liabilities		0
Deferred tax liabilities		5
Pensions and other post-retirement benefit obligations		0
Provisions		0
Non-current liabilities		(27)
Liabilities		(27)
Assets (liabilities)		(27)
Equity
Share capital		0
Share premium account		0
Retained earnings		(99)
Other equity reserves		72
Total shareholders’ equity		(27)
Non-controlling interests		0
Total equity		(27)
Increase (decrease) due to application of IFRS 15 [member]
Non-current assets
Goodwill		0
Other intangible assets		0
Property, plant and equipment		0
Other non-current assets		0
Pension assets		0
Financial and other investments		0
Investments in joint ventures and associates		0
Derivative financial assets		0
Total non-current assets		0
Current assets
Inventories and current intangible assets		0
Trade and other receivables		(3)
Current tax assets		2
Financial and other investments		0
Derivative financial assets		0
Cash and cash equivalents		0
Total current assets		(1)
Assets		(1)
Current liabilities
Borrowings		0
Derivative financial liabilities		0
Trade and other payables		27
Contract liabilities		(21)
Current tax liabilities		0
Provisions		0
Current liabilities		6
Non-current liabilities
Borrowings		0
Derivative financial liabilities		0
Other non-current liabilities		530
Contract liabilities		(776)
Deferred tax liabilities		72
Pensions and other post-retirement benefit obligations		0
Provisions		0
Non-current liabilities		(174)
Liabilities		(168)
Assets (liabilities)		(169)
Equity
Share capital		0
Share premium account		0
Retained earnings		(169)
Other equity reserves		0
Total shareholders’ equity		(169)
Non-controlling interests		0
Total equity		(169)
Currently stated [member]
Non-current assets
Goodwill		5,444
Other intangible assets		899
Property, plant and equipment		39,853
Other non-current assets		115
Pension assets		1,409
Financial and other investments		899
Investments in joint ventures and associates		2,168
Derivative financial assets		1,319
Total non-current assets		52,106
Current assets
Inventories and current intangible assets		341
Trade and other receivables		2,795
Current tax assets		116
Financial and other investments		2,694
Derivative financial assets		405
Cash and cash equivalents		329
Total current assets		6,680
Assets		58,786
Current liabilities
Borrowings		(4,447)
Derivative financial liabilities		(401)
Trade and other payables		(3,426)
Contract liabilities		(21)
Current tax liabilities		(123)
Provisions		(273)
Current liabilities		(8,691)
Non-current liabilities
Borrowings		(22,210)
Derivative financial liabilities		(660)
Other non-current liabilities		(787)
Contract liabilities		(776)
Deferred tax liabilities		(3,559)
Pensions and other post-retirement benefit obligations		(1,672)
Provisions		(1,779)
Non-current liabilities		(31,443)
Liabilities		(40,134)
Assets (liabilities)		18,652
Equity
Share capital		452
Share premium account		1,321
Retained earnings		21,331
Other equity reserves		(4,468)
Total shareholders’ equity		18,636
Non-controlling interests		16
Total equity		£ 18,652

Transition to IFRS 9 and IFRS_4

Transition to IFRS 9 and IFRS 15 IFRS 9: Financial Instruments - Narrative (Details) £ in Millions	Sep. 30, 2018GBP (£)
Financial liabilities at fair value through profit or loss, category [member]
IFRS 9 Reclassification Category [Line Items]
Fair value of financial liabilities previously designated at amortised cost reclassified due to requirements of IFRS 9, initial application of IFRS 9	£ 570
Increase (decrease) in financial liabilities on basis of measurement category, initial application of IFRS 9	32
Retained earnings [member] | Financial liabilities at fair value through profit or loss, category [member]
IFRS 9 Reclassification Category [Line Items]
Increase (decrease) in equity on basis of measurement category initial application of IFRS9	(40)
Fair value of financial liabilities previously designated at AFS reserve reclassified due to requirements of IFRS 9, initial application of IFRS 9	8
Retained earnings [member] | Hedging instruments [member]
IFRS 9 Reclassification Category [Line Items]
Increase (decrease) in equity on basis of measurement category initial application of IFRS9	(67)
Other reserves [member] | Financial liabilities at fair value through profit or loss, category [member]
IFRS 9 Reclassification Category [Line Items]
Increase (decrease) in equity on basis of measurement category initial application of IFRS9	7
Reserve of cash flow hedges [member] | Hedging instruments [member]
IFRS 9 Reclassification Category [Line Items]
Increase (decrease) in equity on basis of measurement category initial application of IFRS9	£ (10)

Transition to IFRS 9 and IFRS_5

Transition to IFRS 9 and IFRS 15 IFRS 15: Revenue from Contracts with Customers - Narrative (Details) - GBP (£)	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	[1]
Disclosure of comparative information prepared under previous GAAP [line items]
Revenue under IFRS 15	£ 5,964,000,000
Operating profit from continuing operations	1,017,000,000	£ 1,274,000,000	[2]
Operating costs	5,330,000,000	£ 5,410,000,000
Increase (decrease) due to application of IFRS 15 [member] | Previous GAAP [member]
Disclosure of comparative information prepared under previous GAAP [line items]
Revenue under IFRS 15	570,000,000
Operating profit from continuing operations	0
Operating costs	570,000,000
US Regulated and UK Gas Transmission [Member] | Increase (decrease) due to application of IFRS 15 [member] | Previous GAAP [member]
Disclosure of comparative information prepared under previous GAAP [line items]
Revenue under IFRS 15	23,000,000
Operating profit from continuing operations	10,000,000
UK Regulated [Member] | Increase (decrease) due to application of IFRS 15 [member] | Previous GAAP [member]
Disclosure of comparative information prepared under previous GAAP [line items]
Revenue under IFRS 15	(6,000,000)
Operating profit from continuing operations	£ (6,000,000)
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).

Additional disclosures in res_3

Additional disclosures in respect of guaranteed securities Narrative (Details) - GBP (£) £ in Millions	Oct. 29, 2007	Sep. 30, 2018	Jun. 01, 2018
Issuer Of Notes - British Transco Finance Inc. [Member]
Disclosure of information about consolidated structured entities [line items]
Borrowings, interest rate			6.625%
Preferred shares, issuance rate	3.90%
Subsidiary Guarantor - National Grid Gas plc [Member]
Disclosure of information about consolidated structured entities [line items]
Preferred shares, issuance rate	3.60%
Issuer Of Notes - Nigara Mohawk Power Coporation [Member] | Preference shares [member]
Disclosure of information about consolidated structured entities [line items]
Proceeds from issuing shares		£ 29

Additional disclosures in res_4

Additional disclosures in respect of guaranteed securities Comprehensive income (Details) - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Disclosure of information about consolidated structured entities [line items]
Revenue		£ 6,347	£ 6,684	[1]
Operating costs		(5,330)	(5,410)	[1]
Operating profit/(loss)		1,017	1,274	[1],[2]
Finance income (cost)		(520)	(514)
Dividend income			0
Share of post-tax results of joint ventures and associates		25	20	[1]
Profit/(loss) before tax		522	780	[1]
Tax		(93)	(153)	[1]
Profit/(loss) after tax from continuing operations		429	627	[1],[3]
Profit/(loss) after tax from discontinued operations		3	50	[1]
Total profit/(loss) for the period (continuing and discontinued)		432	677	[1]
Other comprehensive income for the period, net of tax, from continuing operations		899	255	[3]
Other comprehensive income for the period, net of tax, from discontinued operations2	[4]	36	64	[3]
Total comprehensive income for the period		1,367	996	[3]
Equity shareholders of the parent		1,365	996	[3]
Comprehensive income, attributable to non-controlling interests	[5]	2	0	[3]
Parent Guarantor [Member]
Disclosure of information about consolidated structured entities [line items]
Revenue		0	0
Operating costs		0	0
Operating profit/(loss)		0	0
Finance income (cost)		(109)	81
Dividend income			150
Share of post-tax results of joint ventures and associates		517	461
Profit/(loss) before tax		408	692
Tax		22	(15)
Profit/(loss) after tax from continuing operations		430	677
Profit/(loss) after tax from discontinued operations		0	0
Total profit/(loss) for the period (continuing and discontinued)		430	677
Other comprehensive income for the period, net of tax, from continuing operations		899	255
Other comprehensive income for the period, net of tax, from discontinued operations2		36	64
Total comprehensive income for the period		1,365	996
Equity shareholders of the parent		1,365	996
Comprehensive income, attributable to non-controlling interests		0	0
Issuer Of Notes - Nigara Mohawk Power Coporation [Member]
Disclosure of information about consolidated structured entities [line items]
Revenue		1,149	1,153
Operating costs		(958)	(870)
Operating profit/(loss)		191	283
Finance income (cost)		(58)	(52)
Dividend income			0
Share of post-tax results of joint ventures and associates		0	0
Profit/(loss) before tax		133	231
Tax		(33)	(87)
Profit/(loss) after tax from continuing operations		100	144
Profit/(loss) after tax from discontinued operations		0	0
Total profit/(loss) for the period (continuing and discontinued)		100	144
Other comprehensive income for the period, net of tax, from continuing operations		79	0
Other comprehensive income for the period, net of tax, from discontinued operations2		0	0
Total comprehensive income for the period		179	144
Equity shareholders of the parent		179	144
Comprehensive income, attributable to non-controlling interests		0	0
Other subsidiaries [Member]
Disclosure of information about consolidated structured entities [line items]
Revenue		5,198	5,531
Operating costs		(4,372)	(4,540)
Operating profit/(loss)		826	991
Finance income (cost)		(353)	(543)
Dividend income			0
Share of post-tax results of joint ventures and associates		(36)	5
Profit/(loss) before tax		437	453
Tax		(82)	(51)
Profit/(loss) after tax from continuing operations		355	402
Profit/(loss) after tax from discontinued operations		3	50
Total profit/(loss) for the period (continuing and discontinued)		358	452
Other comprehensive income for the period, net of tax, from continuing operations		416	517
Other comprehensive income for the period, net of tax, from discontinued operations2		0	0
Total comprehensive income for the period		774	969
Equity shareholders of the parent		772	969
Comprehensive income, attributable to non-controlling interests		2	0
Consolidating Adjustments [Member]
Disclosure of information about consolidated structured entities [line items]
Revenue		0	0
Operating costs		0	0
Operating profit/(loss)		0	0
Finance income (cost)		0	0
Dividend income			(150)
Share of post-tax results of joint ventures and associates		(456)	(446)
Profit/(loss) before tax		(456)	(596)
Tax		0	0
Profit/(loss) after tax from continuing operations		(456)	(596)
Profit/(loss) after tax from discontinued operations		0	0
Total profit/(loss) for the period (continuing and discontinued)		(456)	(596)
Other comprehensive income for the period, net of tax, from continuing operations		(495)	(517)
Other comprehensive income for the period, net of tax, from discontinued operations2		0	0
Total comprehensive income for the period		(951)	(1,113)
Equity shareholders of the parent		(951)	(1,113)
Comprehensive income, attributable to non-controlling interests		£ 0	£ 0
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[3]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[4]	The other comprehensive income from discontinued operations relates to items of other comprehensive income of Cadent (investment held through Quadgas Holdco Limited), comprising £35m (2017: £60m) remeasurement gains on pension assets and post-retirement benefit obligations, and £1m (2017: £4m) net gains in respect of cash flow hedges. Both items are shown net of tax.
[5]	The non-controlling interests for the six month periods ending 30 September 2018 and 30 September 2017 relate to continuing operations.

Additional disclosures in res_5

Additional disclosures in respect of guaranteed securities Balance sheet (Details) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Disclosure of information about consolidated structured entities [line items]
Goodwill	£ 5,860	£ 5,444
Other intangible assets	990	899
Property, plant and equipment	42,661	39,853
Other non-current assets	96	115
Amounts owed by subsidiary undertakings, non-current	0	0
Pension assets	1,754	1,409
Financial and other investments	1,283	3,067
Derivative financial assets	1,159	1,319
Total non-current assets	53,803	52,106
Inventories and current intangible assets	440	341
Trade and other receivables	2,335	2,798
Current tax assets	89	114
Amounts owed by subsidiary undertakings, current	0	0
Financial and other investments	1,658	2,694	£ 2,573	£ 8,741
Derivative financial assets	189	405
Cash and cash equivalents	130	329	39	1,139
Assets held for sale	2,121	0
Total current assets	6,962	6,681
Total assets	60,765	58,787
Borrowings	(4,134)	(4,447)
Derivative financial liabilities	(355)	(401)
Trade and other payables	(3,144)	(3,453)
Contract liabilities	(26)	0
Current payables to related parties	0	0
Current tax liabilities	(137)	(123)
Provisions	(379)	(273)
Liabilities held for sale	(50)	0
Current liabilities	(8,225)	(8,697)
Borrowings	(23,510)	(22,178)
Derivative financial liabilities	(780)	(660)
Other non-current liabilities	(868)	(1,317)
Contract liabilities	(834)	0
Non-current payables to related parties	0	0
Deferred tax liabilities	(3,902)	(3,636)
Non-current provisions for employee benefits	(1,424)	(1,672)
Other non-current provisions	(1,887)	(1,779)
Non-current liabilities	33,205	31,242
Liabilities	(41,430)	(39,939)
Net assets	19,335	18,848
Share capital	457	452
Share premium account	1,316	1,321
Retained earnings	21,587	21,599
Other equity reserves	(4,043)	(4,540)
Total shareholders’ equity	19,317	18,832
Non-controlling interests	18	16
Total equity	19,335	18,848	£ 16,872	£ 20,384
Parent Guarantor [Member]
Disclosure of information about consolidated structured entities [line items]
Goodwill	0	0
Other intangible assets	0	0
Property, plant and equipment	0	0
Other non-current assets	9	0
Amounts owed by subsidiary undertakings, non-current	352	350
Pension assets	0	0
Financial and other investments	22,983	21,708
Derivative financial assets	8	18
Total non-current assets	23,352	22,076
Inventories and current intangible assets	0	0
Trade and other receivables	0	0
Current tax assets	0	0
Amounts owed by subsidiary undertakings, current	12,710	11,253
Financial and other investments	718	939
Derivative financial assets	546	308
Cash and cash equivalents	67	0
Assets held for sale	0
Total current assets	14,041	12,500
Total assets	37,393	34,576
Borrowings	(832)	(779)
Derivative financial liabilities	(58)	(187)
Trade and other payables	(64)	(62)
Contract liabilities	0
Current payables to related parties	(14,000)	(11,810)
Current tax liabilities	0	0
Provisions	0	0
Liabilities held for sale	0
Current liabilities	(14,954)	(12,838)
Borrowings	(782)	(773)
Derivative financial liabilities	(232)	(41)
Other non-current liabilities	0	0
Contract liabilities	0
Non-current payables to related parties	(2,108)	(2,092)
Deferred tax liabilities	0	0
Non-current provisions for employee benefits	0	0
Other non-current provisions	0	0
Non-current liabilities	3,122	2,906
Liabilities	(18,076)	(15,744)
Net assets	19,317	18,832
Share capital	457	452
Share premium account	1,316	1,321
Retained earnings	21,587	21,599
Other equity reserves	(4,043)	(4,540)
Total shareholders’ equity	19,317	18,832
Non-controlling interests	0	0
Total equity	19,317	18,832
Issuer Of Notes - Nigara Mohawk Power Coporation [Member]
Disclosure of information about consolidated structured entities [line items]
Goodwill	743	691
Other intangible assets	3	3
Property, plant and equipment	6,769	6,148
Other non-current assets	6	3
Amounts owed by subsidiary undertakings, non-current	0	0
Pension assets	268	231
Financial and other investments	34	30
Derivative financial assets	6	2
Total non-current assets	7,829	7,108
Inventories and current intangible assets	61	36
Trade and other receivables	574	515
Current tax assets	0	0
Amounts owed by subsidiary undertakings, current	84	130
Financial and other investments	2	15
Derivative financial assets	11	7
Cash and cash equivalents	3	4
Assets held for sale	0
Total current assets	735	707
Total assets	8,564	7,815
Borrowings	(625)	(51)
Derivative financial liabilities	(6)	(36)
Trade and other payables	(323)	(318)
Contract liabilities	0
Current payables to related parties	(36)	0
Current tax liabilities	(217)	(202)
Provisions	(20)	(23)
Liabilities held for sale	0
Current liabilities	(1,227)	(630)
Borrowings	(1,667)	(2,087)
Derivative financial liabilities	(6)	(18)
Other non-current liabilities	(472)	(281)
Contract liabilities	0
Non-current payables to related parties	0	0
Deferred tax liabilities	(694)	(626)
Non-current provisions for employee benefits	(757)	(765)
Other non-current provisions	(280)	(248)
Non-current liabilities	3,876	4,025
Liabilities	(5,103)	(4,655)
Net assets	3,461	3,160
Share capital	144	133
Share premium account	2,362	2,194
Retained earnings	954	830
Other equity reserves	1	3
Total shareholders’ equity	3,461	3,160
Non-controlling interests	0	0
Total equity	3,461	3,160
Other subsidiaries [Member]
Disclosure of information about consolidated structured entities [line items]
Goodwill	5,117	4,753
Other intangible assets	987	896
Property, plant and equipment	35,892	33,705
Other non-current assets	90	112
Amounts owed by subsidiary undertakings, non-current	2,109	2,092
Pension assets	1,486	1,178
Financial and other investments	3,779	5,221
Derivative financial assets	1,145	1,299
Total non-current assets	50,605	49,256
Inventories and current intangible assets	379	305
Trade and other receivables	1,761	2,283
Current tax assets	298	307
Amounts owed by subsidiary undertakings, current	13,949	11,777
Financial and other investments	938	1,740
Derivative financial assets	99	46
Cash and cash equivalents	60	325
Assets held for sale	2,121
Total current assets	19,605	16,783
Total assets	70,210	66,039
Borrowings	(2,677)	(3,617)
Derivative financial liabilities	(758)	(134)
Trade and other payables	(2,757)	(3,073)
Contract liabilities	(26)
Current payables to related parties	(12,707)	(11,350)
Current tax liabilities	(129)	(114)
Provisions	(359)	(250)
Liabilities held for sale	(50)
Current liabilities	(19,463)	(18,538)
Borrowings	(21,061)	(19,318)
Derivative financial liabilities	(542)	(601)
Other non-current liabilities	(396)	(1,036)
Contract liabilities	(834)
Non-current payables to related parties	(353)	(350)
Deferred tax liabilities	(3,217)	(3,010)
Non-current provisions for employee benefits	(667)	(907)
Other non-current provisions	(1,607)	(1,531)
Non-current liabilities	28,677	26,753
Liabilities	(48,140)	(45,291)
Net assets	22,070	20,748
Share capital	180	180
Share premium account	9,032	9,032
Retained earnings	12,732	11,511
Other equity reserves	108	9
Total shareholders’ equity	22,052	20,732
Non-controlling interests	18	16
Total equity	22,070	20,748
Consolidating Adjustments [Member]
Disclosure of information about consolidated structured entities [line items]
Goodwill	0	0
Other intangible assets	0	0
Property, plant and equipment	0	0
Other non-current assets	(9)	0
Amounts owed by subsidiary undertakings, non-current	(2,461)	(2,442)
Pension assets	0	0
Financial and other investments	(25,513)	(23,892)
Derivative financial assets	0	0
Total non-current assets	(27,983)	(26,334)
Inventories and current intangible assets	0	0
Trade and other receivables	0	0
Current tax assets	(209)	(193)
Amounts owed by subsidiary undertakings, current	(26,743)	(23,160)
Financial and other investments	0	0
Derivative financial assets	(467)	44
Cash and cash equivalents	0	0
Assets held for sale	0
Total current assets	(27,419)	(23,309)
Total assets	(55,402)	(49,643)
Borrowings	0	0
Derivative financial liabilities	467	(44)
Trade and other payables	0	0
Contract liabilities	0
Current payables to related parties	26,743	23,160
Current tax liabilities	209	193
Provisions	0	0
Liabilities held for sale	0
Current liabilities	27,419	23,309
Borrowings	0	0
Derivative financial liabilities	0	0
Other non-current liabilities	0	0
Contract liabilities	0
Non-current payables to related parties	2,461	2,442
Deferred tax liabilities	9	0
Non-current provisions for employee benefits	0	0
Other non-current provisions	0	0
Non-current liabilities	(2,470)	(2,442)
Liabilities	29,889	25,751
Net assets	(25,513)	(23,892)
Share capital	(324)	(313)
Share premium account	(11,394)	(11,226)
Retained earnings	(13,686)	(12,341)
Other equity reserves	(109)	(12)
Total shareholders’ equity	(25,513)	(23,892)
Non-controlling interests	0	0
Total equity	£ (25,513)	£ (23,892)

Additional disclosures in res_6

Additional disclosures in respect of guaranteed securities Cash flow statement (Details) - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Disclosure of information about consolidated structured entities [line items]
Net cash flow from operating activities – continuing operations		£ 1,935	£ 2,068	[1]
Net cash flow (used in)/from operating activities – discontinued operations	[1],[2]	(47)	(126)
Net cash flow (used in)/from investing activities – continuing operations		(788)	4,224	[1]
Cash flows from (used in) investing activities, discontinued operations	[3]	78	15	[1]
Net cash flow used in financing activities – continuing operations		(1,380)	(7,049)	[1]
Net cash flow (used in)/from financing activities – discontinued operations	[2],[4]	0	(231)	[1]
Net decrease in cash and cash equivalents		(202)	(1,099)	[1]
Parent Guarantor [Member]
Disclosure of information about consolidated structured entities [line items]
Net cash flow from operating activities – continuing operations		2	24
Net cash flow (used in)/from operating activities – discontinued operations	[1]	0	0
Net cash flow (used in)/from investing activities – continuing operations		(265)	3,193
Cash flows from (used in) investing activities, discontinued operations		0	0
Net cash flow used in financing activities – continuing operations		330	(4,303)
Net cash flow (used in)/from financing activities – discontinued operations	[2]	0	0
Net decrease in cash and cash equivalents		67	(1,086)
Issuer Of Notes - Nigara Mohawk Power Coporation [Member]
Disclosure of information about consolidated structured entities [line items]
Net cash flow from operating activities – continuing operations		236	328
Net cash flow (used in)/from operating activities – discontinued operations	[1]	0	0
Net cash flow (used in)/from investing activities – continuing operations		(171)	155
Cash flows from (used in) investing activities, discontinued operations		0	0
Net cash flow used in financing activities – continuing operations		(65)	(482)
Net cash flow (used in)/from financing activities – discontinued operations	[2]	0	0
Net decrease in cash and cash equivalents		0	1
Other subsidiaries [Member]
Disclosure of information about consolidated structured entities [line items]
Net cash flow from operating activities – continuing operations		1,697	1,716
Net cash flow (used in)/from operating activities – discontinued operations	[1]	(47)	(126)
Net cash flow (used in)/from investing activities – continuing operations		(545)	596
Cash flows from (used in) investing activities, discontinued operations		78	15
Net cash flow used in financing activities – continuing operations		(1,452)	(1,984)
Net cash flow (used in)/from financing activities – discontinued operations	[2]	0	(231)
Net decrease in cash and cash equivalents		(269)	(14)
Consolidating Adjustments [Member]
Disclosure of information about consolidated structured entities [line items]
Net cash flow from operating activities – continuing operations		0	0
Net cash flow (used in)/from operating activities – discontinued operations	[1]	0	0
Net cash flow (used in)/from investing activities – continuing operations		193	280
Cash flows from (used in) investing activities, discontinued operations		0	0
Net cash flow used in financing activities – continuing operations		(193)	(280)
Net cash flow (used in)/from financing activities – discontinued operations	[2]	0	0
Net decrease in cash and cash equivalents		£ 0	£ 0
[1]	Comparatives have been re-presented to reflect the classification of our retained interest in Quadgas HoldCo Limited as a discontinued operation in the current period (see note 6).
[2]	Cash flows used in discontinued operating activities in both 2018 and 2017 related to the disposal of the UK Gas Distribution business.
[3]	Cash flows from discontinued investing activities relates to the receipt of £66m (2017: £nil) of dividends and £12m (2017: £15m) of interest on the shareholder loan from our investment in Quadgas HoldCo Limited (see note 6).
[4]	Cash flows used in discontinued financing activities in 2017 related to the liability management programme related to the UK Gas Distribution business.