British Telecommunications 6-K 23 Nov 18 2018 H1 Current report (foreign) Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Sep. 30, 2018
Document - Document and Entity Information [Abstract]
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	H1
Entity Registrant Name	BRITISH TELECOMMUNICATIONS PLC /ADR
Entity Central Index Key	820,534
Current Fiscal Year End Date	--03-31

Group income statement

Group income statement - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Revenue	£ 11,588	£ 11,786
Operating costs	(9,896)	(10,332)
Operating profit	1,692	1,454
Finance expense	(386)	(381)
Finance income	147	101
Net finance expense	(239)	(280)
Share of post tax profit of associates and joint ventures	1
Profit before tax	1,454	1,174
Tax	(310)	(293)
Profit for the period	1,144	881
Before Specific Items [member]
Revenue	11,624	11,800
Operating costs	(9,684)	(9,959)
Operating profit	1,940	1,841
Finance expense	(317)	(272)
Finance income	147	101
Net finance expense	(170)	(171)
Share of post tax profit of associates and joint ventures	1
Profit before tax	1,771	1,670
Tax	(362)	(339)
Profit for the period	1,409	1,331
Specific items [member]
Revenue	(36)	(14)
Operating costs	(212)	(373)
Operating profit	(248)	(387)
Finance expense	(69)	(109)
Net finance expense	(69)	(109)
Profit before tax	(317)	(496)
Tax	52	46
Profit for the period	£ (265)	£ (450)

Group statement of comprehensiv

Group statement of comprehensive income - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of comprehensive income [abstract]
Profit for the period	£ 1,144	£ 881
Items that will not be reclassified to the income statement
Remeasurements of the net pension obligation	(292)	(4)
Tax on pension remeasurements	58	17
Items that have been or may be reclassified subsequently to the income statement
Exchange differences on translation of foreign operations	74	(115)
Fair value movements on available-for-sale assets	5	4
Fair value movements on cash flow hedges:
- net fair value (losses) gains	477	(49)
- recognised in income and expense	(293)	78
Movement on cost of hedging reserve	(90)
Tax on components of other comprehensive income that have been or may be reclassified	(30)	(9)
Other comprehensive profit (loss) for the period, net of tax	(91)	(78)
Total comprehensive income for the period	£ 1,053	£ 803

Group balance sheet

Group balance sheet - GBP (£) £ in Millions		Sep. 30, 2018	Mar. 31, 2018	[1]
Non-current assets
Intangible assets		£ 14,618	£ 14,455
Property, plant and equipment		17,234	17,000
Derivative financial instruments		1,467	1,312
Investments		13,569	13,354
Associates and joint ventures		43	38
Trade and other receivables		436	317
Contract assets	[2]	239
Deferred tax assets		1,003	1,326
Non current assets		48,609	47,802
Current assets
Programme rights		727	272
Inventories		305	239
Trade and other receivables		3,570	4,029
Contract assets	[2]	1,321
Assets held for sale		88
Current tax receivable		77	77
Derivative financial instruments		311	197
Investments		3,494	3,224
Cash and cash equivalents		421	521
Current assets		10,314	8,559
Current liabilities
Loans and other borrowings		4,290	2,298
Derivative financial instruments		53	50
Trade and other payables		5,771	7,190
Contract liabilities	[2]	1,343
Current tax liabilities		211	83
Provisions		607	603
Current liabilities		12,275	10,224
Total assets less current liabilities		46,648	46,137
Non-current liabilities
Loans and other borrowings		15,317	13,038
Derivative financial instruments		706	787
Contract liabilities	[2]	121
Retirement benefit obligations		5,280	6,847
Other payables		1,563	1,326
Deferred tax liabilities		1,176	1,340
Provisions		486	452
Non current liabilities		24,649	23,790
Equity
Share capital		2,172	2,172
Share premium		8,000	8,000
Other reserves		1,384	1,241
Retained earnings		10,443	10,934
Total equity		21,999	22,347
Total equity and Liabilities		£ 46,648	£ 46,137
[1]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements
[2]	Contract assets and contract liabilities arise following the adoption of IFRS 15 on 1 April 2018. See note 1 to the condensed consolidated financial statements.

Group Statement of Changes in E

Group Statement of Changes in Equity - GBP (£) £ in Millions		Total		Share capital [member]	Share premium [member]	Other reserves [member]	Retained earnings [member]		Share capital [member]	Share premium [member]	Other reserves [member]	Retained earnings [member]
Beginning balance at Mar. 31, 2017		£ 18,926							£ 2,172	£ 8,000	£ 1,591	£ 7,163
Profit for the period		881										881
Other comprehensive income (loss) before tax		(164)									(160)	(4)
Tax on other comprehensive (loss) income		8									(9)	17
Transferred to the income statement		78									78
Comprehensive (loss) income		803									(91)	894
Share-based payments		40										40
Other movements		3										3
Ending balance at Sep. 30, 2017		19,772							2,172	8,000	1,500	8,100
Beginning balance at Mar. 31, 2017		18,926							2,172	8,000	1,591	7,163
Profit for the period | Previously reported [member]		2,184
Profit for the period | Restated [member]		2,184
Transferred to the income statement | Previously reported [member]		277
Transferred to the income statement | Restated [member]		277
Comprehensive (loss) income | Previously reported [member]		3,731
Comprehensive (loss) income | Pension adjustments [member]		(393)
Comprehensive (loss) income | Restated [member]		3,338
Ending balance (Previously reported [member]) at Mar. 31, 2018		22,740		£ 2,172	£ 8,000	£ 1,241	£ 11,327		2,172	8,000	1,241	11,327
Ending balance (Pension adjustments [member]) at Mar. 31, 2018		(393)
Ending balance (Restated [member]) at Mar. 31, 2018		22,347		2,172	8,000	1,241	10,934		2,172	8,000	1,241	10,934
Ending balance at Mar. 31, 2018	[1]	22,347
IFRS opening balance adjustment		1,308	[2]				1,308	[2]				1,308
Tax on IFRS opening balance adjustment		(248)	[2]				(248)	[2]				(248)
Ending balance at Apr. 01, 2018		23,407		2,172	8,000	1,241	11,994		2,172	8,000	1,241	11,994
Beginning balance (Previously reported [member]) at Mar. 31, 2018		22,740		2,172	8,000	1,241	11,327		2,172	8,000	1,241	11,327
Beginning balance (Pension adjustments [member]) at Mar. 31, 2018		(393)
Beginning balance (Restated [member]) at Mar. 31, 2018		22,347		2,172	8,000	1,241	10,934		£ 2,172	£ 8,000	£ 1,241	£ 10,934
Beginning balance at Mar. 31, 2018	[1]	22,347
Profit for the period		1,144					1,144
Other comprehensive income (loss) before tax		264				556	(292)
Movements on cost of hedging reserve		(90)				(90)
Tax on other comprehensive (loss) income		28				(30)	58
Transferred to the income statement		(293)				(293)
Comprehensive (loss) income		1,053				143	910
Dividends		(2,500)					(2,500)
Share-based payments		36					36
Unclaimed dividends over 10 years		5					5
Other movements		(2)					(2)
Ending balance at Sep. 30, 2018		£ 21,999		£ 2,172	£ 8,000	£ 1,384	£ 10,443
[1]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements
[2]	See Note 1 to the condensed consolidated financial statements

Group Cash Flow Statement

Group Cash Flow Statement - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Cash flow from operating activities
Profit before tax		£ 1,454	£ 1,174
Share-based payments		36	40
Profit on disposal of subsidiaries and interest in associates			(1)
Share of post tax losses of associates and joint ventures		(1)
Net finance expense		239	280
Depreciation and amortisation		1,736	1,757
(Increase) decrease in working capital		(489)	(431)
Provisions, pensions and other non-cash movements	[1]	(2,009)	(72)
Cash inflow from operating activities	[2]	966	2,747
Tax paid		(210)	(181)
Net cash inflow from operating activities		756	2,566
Cash flow from investing activities
Interest received		8	2
Acquisition of subsidiaries, associates and joint ventures		(6)	(20)
Proceeds on disposal of subsidiaries			2
Purchases of property, plant and equipment and software		(1,739)	(1,665)
Proceeds on disposal of property, plant and equipment		3	11
Outflow non-current amounts to ultimate parent company	[3]	(1,052)	(1,200)
Purchases of current financial assets		(6,721)	(5,892)
Proceeds on disposal of current financial assets		6,395	4,853
Net cash outflow from investing activities		(3,112)	(3,909)
Cash flow from financing activities
Interest paid		(236)	(259)
Proceeds from bank loans and bonds		2,896	2,029
Repayment of borrowings	[4]	(480)	(502)
Cash flows from derivatives related to net debt		59	(132)
Net cash outflow from financing activities		2,239	1,136
Net (decrease) increase in cash and cash equivalents		(117)	(207)
Opening cash and cash equivalents		492	509
Net (decrease) increase in cash and cash equivalents		(117)	(207)
Effect of exchange rate changes		7	(19)
Closing cash and cash equivalents	[5]	£ 382	£ 283
[1]	Includes pension deficit payments of £2,012m for the half year to 30 September 2018 (H1 2017/18: £10m)
[2]	Includes cash flows relating to TV programme rights
[3]	In addition, there are non-cash movements in this intra-group loan arrangement which principally relate to the settlement of dividends with the parent company and amounts the ultimate parent company was owed by the parent company which were settled through their loan accounts with British Telecommunications plc. For further details see note 12.
[4]	Repayment of borrowings includes the impact of hedging and repayment of lease liabilities
[5]	Net of bank overdrafts of £39m at 30 September 2018 (30 September 2017: £62m; 31 March 2018: £29m)

Group Cash Flow Statement (Pare

Group Cash Flow Statement (Parenthetical) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Statement of cash flows [abstract]
Pension deficit payments	£ 2,012	£ 10
Net of bank overdrafts	£ 39	£ 62	£ 29

Basis of preparation and accoun

Basis of preparation and accounting policies	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Basis of preparation and accounting policies	1 Basis of preparation and accounting policies These condensed consolidated financial statements (‘the financial statements’) comprise the financial results of British Telecommunications plc for the half years to 30 September 2018 and 30 September 2017 together with the balance sheet at 31 March 2018. The financial statements for the half year to 30 September 2018 have been reviewed by the auditors and their review opinion is on page 26. The financial statements have been prepared in accordance with the Disclosure Guidance and Transparency Rules sourcebook (DTR) of the Financial Conduct Authority and with IAS 34 Interim Financial Reporting 20-F 20-F(A) Having assessed the principal risks, the directors consider it appropriate to adopt the going concern basis of accounting in preparing the financial statements. Except as described below and other than income taxes which are accrued using the tax rate that is expected to be applicable for the full financial year, the financial statements have been prepared in accordance with the accounting policies as set out in the financial statements for the year to 31 March 2018 and have been prepared under the historical cost convention as modified by the revaluation of financial assets and liabilities (including derivative financial instruments) at fair value. The comparative figures for the financial year ended 31 March 2018 are not the company’s statutory accounts for that financial year. Those accounts have been reported on by the company’s auditor and delivered to the registrar of companies. The report of the auditor was unqualified, did not include a reference to any matters to which the auditor drew attention by way of emphasis without qualifying their report, and did not contain a statement under section 498 (2) or (3) of the Companies Act 2006. New and amended accounting standards effective during the year The following standards have been issued and were effective for BT from 1 April 2018: IFRS 15 ‘Revenue from contracts with customers’ Background IFRS 15 sets out the requirements for recognising revenue and costs from contracts with customers and includes extensive disclosure requirements. The standard requires entities to apportion revenue earned from contracts to individual performance obligations, on a relative stand-alone selling price basis, based on a five-step model. As disclosed in our Annual Report 2018 we have adopted the standard on a modified retrospective basis and have recognised the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings at 1 April 2018. Under this transition method: – the standard has been applied only to contracts in progress but not completed at the date of initial application; – for contracts that were modified before 1 April 2018, we have reflected the aggregate effect of all of the modifications that occur before this date at 1 April 2018; – we have not restated prior year comparatives for the effect of IFRS 15 but have instead restated our 1 April 2018 opening retained earnings for the full cumulative impact of adopting this standard; and – for the year ended 31 March 2019 we will provide a reconciliation of our primary financial statements under IFRS 15 to those in accordance with IAS 18 in our Annual Report & Form 20-F Financial impact In our Annual Report 2018 we estimated that the likely impact on transition at 1 April 2018 would produce a cumulative increase in retained earnings of between £1.1bn and £1.5bn before tax. The actual increase of £1.3bn before tax (£1.1bn after tax) has primarily been recorded as a contract asset and will lead to an additional one-off cash tax payment of £0.2bn equally split between 2018/19 and 2019/20. The cumulative increase in retained earnings is mainly due to the acceleration of handset revenues and, to a lesser extent, deferral of costs (notably third party contract acquisition costs primarily associated with post pay mobile contracts). The financial impact of each business area is as follows: – Under our previous accounting policy, mobile handset revenue was recognised based on the amount the customer pays for the handset when it is delivered to the customer. Generally mobile handsets are either provided free or for a small upfront charge. Under IFRS 15, additional revenue is allocated to the mobile handset at the start of the contract. This is calculated with reference to its relative standalone value within the contract, regardless of the contract pricing. For each mobile handset contract the revenue recognition profile changed with greater day one recognition of revenue for the handset and a corresponding reduction in ongoing mobile service revenue over the contract period. The difference between the mobile handset revenue recognised and the amounts charged to the customer has been recognised as a contract asset. Over time, we expect the contract asset generated to remain at similar levels as old contracts expire and new ones are signed. However, we will see short-term volatility, for example around key handset launches. This primarily impacted Consumer, and to a lesser extent this also impacted mobile handset revenues in Business and Public Sector in respect of the legacy EE business division. We saw a similar trend in respect of subsidised equipment although this had a less significant impact due to the lower relative standalone value for this equipment. – Previously, sales commissions and other third party acquisition costs resulting directly from securing contracts with customers were expensed when incurred. Under IFRS 15 sales commissions and other third party contract acquisition costs are recognised as an asset, and amortised over the period in which the corresponding benefit is received, resulting in earlier profit recognition. The impact is greatest in Consumer in respect of third-party acquisition costs. – The above two impacts are partly offset by amended accounting for connections revenue. Previously, the group recognised connections revenue upon performance of the connection activity. Under IFRS 15 connections revenue is deferred and recognised on a straight-line basis over the associated line/circuit contractual period. This means that revenue and profits are recognised later. On transition this led to the recognition of a contract liability as revenue and profits are deferred to future periods. Wholesale and Ventures and Openreach deliver the majority of this service and therefore experienced the majority of the impact. Over time, this liability is expected to remain at similar levels as old contracts expire and new ones are signed. – The IFRS 15 impact on other areas was not material. This included certain contract fulfilment costs which are recognised as an asset and amortised over the period in which benefit is received and certain expenses are recognised as a deduction from revenue. Pro forma We have prepared and published unaudited pro forma results for the years ended 31 March 2018 and 31 March 2017 under IFRS 15. While BT believes the pro forma information contained in this document to be reliable, BT does not warrant the accuracy, completeness or validity of the information, figures or calculations and shall not be liable in any way for loss or damage arising out of the use of the information, or any errors or omissions in its content. IFRS 9 ‘Financial Instruments’ IFRS 9 is applicable to financial assets and financial liabilities and covers the classification, measurement, impairment and de- There are no other new or amended standards or interpretations adopted during the year that have a significant impact on the group. New and amended accounting standards that have been issued but are not yet effective IFRS 16 ‘Leases’ We will report our financial statements under IFRS 16 from the first quarter of 2019/20. We expect to adopt IFRS 16 on a modified retrospective basis in our 2019/20 financial statements. Accordingly we will not restate prior year comparatives for the effect of IFRS 16 but will instead restate our 1 April 2019 opening reserves for the full cumulative impact of adopting this standard. The standard requires lessees to recognise assets and liabilities for all leases unless the lease term is 12 months or less, or the underlying asset is of low value. We are still in the process of quantifying the implications of this standard. However, we expect the following indicative impacts: – there is expected to be an increase in total assets, as leased assets which are currently accounted for off balance sheet (i.e. classified as operating leases under IAS 17) will be recognised on balance sheet and valued in accordance with the principles of IFRS 16. The biggest asset category impacted for the group is expected to be land and buildings – there is expected to be an increase in debt, as liabilities relating to existing operating leases are recognised – operating lease expenditure will be reclassified and split between depreciation and finance costs. Therefore EBITDA will increase. Future depreciation and finance costs are also expected to increase as a result of increased assets and liabilities – there is an expected temporary reduction in profit after tax. This is expected to be driven by an increase in finance costs as a result of the new leases. These finance costs will have an accelerated profile which will reduce over the lease term – there may be a corresponding effect on tax balances in relation to all of the above impacts. This standard will require us to make key accounting judgements in particular around the likelihood of lease renewals. Details of our existing operating lease commitments at 31 March 2018 are set out in note 30 of our Annual Report 2018.

Restatement of prior period fin

Restatement of prior period financial statements	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Restatement of prior period financial statements	2 Restatement of prior period financial statements IAS 19 accounting valuation of retirement benefit obligations On 27 July 2018, we announced that we had been alerted to an error made by our independent external actuary in the actuary’s calculation of our IAS 19 accounting valuation of retirement benefit obligations at 31 March 2018. Our independent external actuary is employed as an expert to calculate the IAS 19 accounting valuation on behalf of management. The error resulted from the incorrect application of changes to demographic assumptions. Management determined that the error was material with respect to our Group statement of comprehensive income and would require the Group to restate its previously issued consolidated financial statements for year ended 31 March 2018. The accounting error understated the net pension obligation, after tax, at 31 March 2018 by £393m (£476m gross of deferred tax) and overstated total equity in the balance sheet by £393m. The re-measurement re-measurement The error has no effect on the Group income statement or the Group cash flow statement or any amounts included in the financial statements for the years ending 31 March 2017 and 31 March 2016 or the six months to 30 September 2017. It also has no effect on the 2017 triennial funding valuation of the BT Pension Scheme, associated cash contributions or on the pension scheme members. The impact of the retirement benefit obligation restatement and the IFRS 15 and IFRS 9 opening balance adjustment have been set out in the reconciliations below: Group statement of comprehensive income Year to 31 March 2018 As published Pensions Restated Profit for the period 2,184 - 2,184 Other comprehensive income (loss) Items that will not be reclassified to the income statement: Remeasurements of the net pension obligation 2,160 (476 ) 1,684 Tax on pension remeasurements (346 ) 83 (263 ) Items that have been or may be reclassified subsequently to the income statement: Exchange differences on translation of foreign operations (188 ) - (188 ) Fair value movements on available-for-sale 11 - 11 Fair value movements on cash flow hedges: - net fair value (losses) gains (368 ) - (368 ) - recognised in income and expense 277 - 277 Movement on cost of hedging reserve - - - Tax on components of other comprehensive income that have been or may be reclassified 1 - 1 Other comprehensive profit (loss) for the period, net of tax 1,547 (393 ) 1,154 Total comprehensive income (loss) for the period 3,731 (393 ) 3,338 Group balance sheet At 31 March as published Pension At 31 March 2018 restated IFRS 1 At 1 April £m £m £m £m £m Non-current Intangible assets 14,455 - 14,455 - 14,455 Property, plant and equipment 17,000 - 17,000 - 17,000 Investments 13,354 - 13,354 - 13,354 Trade and other receivables 317 - 317 114 431 Contract assets - - - 198 198 Deferred tax assets 1,243 83 1,326 - 1,326 Other non-current 1,350 1,350 - 1,350 47,719 83 47,802 312 48,114 Current assets Trade and other receivables 4,029 - 4,029 (337) 3,692 Contract assets - - - 1,417 1,417 Cash and cash equivalents 521 - 521 - 521 Other current assets 4,009 - 4,009 - 4,009 8,559 - 8,559 1,080 9,639 Current liabilities Loans and other borrowings 2,298 - 2,298 - 2,298 Trade and other payables 7,190 - 7,190 (1,409) 5,781 Contract liabilities - - - 1,406 1,406 Current tax liabilities 83 - 83 248 331 Other current liabilities 653 - 653 - 653 10,224 - 10,224 245 10,469 Total assets less current liabilities 46,054 83 46,137 1,147 47,284 Non-current Loans and other borrowings 13,038 - 13,038 - 13,038 Retirement benefit obligations 6,371 476 6,847 - 6,847 Other non-current 3,905 - 3,905 87 3,992 23,314 476 23,790 87 23,877 Equity Share capital 2,172 - 2,172 - 2,172 Share premium 8,000 - 8,000 - 8,000 All other reserves 1,241 - 1,241 - 1,241 Retained earnings 11,327 (393) 10,934 1,060 11,994 Total equity 22,740 (393) 22,347 1,060 23,407 46,054 83 46,137 1,147 47,284 Group statement of changes in equity Share Share Other Retained Total £m £m £m £m £m At 31 March 2018 - as published 2,172 8,000 1,241 11,327 22,740 Pension restatement - - - (393) (393) At 31 March 2018 – restated 2,172 8,000 1,241 10,934 22,347 IFRS opening balance adjustment 1 - - - 1,308 1,308 Tax on IFRS opening balance adjustment 1 - - - (248) (248) At 1 April 2018 2,172 8,000 1,241 11,994 23,407 1 This reflects the opening balance sheet adjustment for both IFRS 15 and IFRS 9. See note 1 to the condensed consolidated financial statements

Operating results - by customer

Operating results - by customer facing unit	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Operating results - by customer facing unit	3 Operating results – by customer facing unit External Internal Group EBITDA 1 Operating Half year to 30 September 2018 (IFRS 15 basis) £m £m £m £m £m Consumer 5,220 52 5,272 1,221 713 Business and Public Sector 2 2,140 55 2,195 708 529 Wholesale and Ventures 2 873 56 929 325 173 Global Services 2,332 - 2,332 208 22 Openreach 1,057 1,415 2,472 1,177 498 Other 2 - 2 37 5 Intra-group items - (1,578 ) (1,578 ) - - Total adjusted 3 11,624 - 11,624 3,676 1,940 Specific items (note 6) (36 ) (248 ) Total 11,588 1,692 Half year to 30 September 2017 (IAS 18 basis) Consumer (restated) 4 5,083 50 5,133 1,139 654 Business and Public Sector 2,224 57 2,281 694 509 Wholesale and Ventures 926 71 997 361 207 Global Services 2,506 - 2,506 154 (67 ) Openreach 1,054 1,494 2,548 1,238 548 Other 7 - 7 12 (10 ) Intra-group items - (1,672 ) (1,672 ) - - Total adjusted 3 11,800 - 11,800 3,598 1,841 Specific items (note 6) (14 ) (387 ) Total 11,786 1,454 1 2 3 4

Operating result - by type of r

Operating result - by type of revenue	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Operating result - by type of revenue	4 Operating result – by type of revenue 1 Half year to 30 September 2018 2017 £m £m ICT and managed networks 2,203 2,256 Fixed access subscription revenue 4,641 4,814 Mobile subscription revenue 2,659 3,086 Equipment and other services 2,121 1,644 Total adjusted 2 11,624 11,800 Specific items (note 6) (36) (14) Total 11,588 11,786 1 re-presented 2

Operating costs

Operating costs	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Operating costs	5 Operating costs Half year 2018 (IFRS 15) 2017 (IAS 18) £m £m Direct labour costs 2,663 2,688 Indirect labour costs 472 451 Leaver costs 8 30 Total labour costs 3,143 3,169 Capitalised labour (729 ) (668 ) Net labour costs 2,414 2,501 Product costs and sales commissions 1 2,172 2,153 Payments to telecommunications operators 1,073 1,207 Property and energy costs 661 649 Network operating and IT costs 508 476 Programme rights charges 403 377 Other operating costs 1 717 839 Operating costs before depreciation, amortisation and specific items 7,948 8,202 Depreciation and amortisation 1,736 1,757 Total operating costs before specific items 9,684 9,959 Specific items (Note 6) 212 373 Total operating costs 9,896 10,332 1 Other operating costs have been disaggregated and re-presented

Specific items

Specific items	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Specific items	6 Specific items The group separately identifies and discloses those items that in management’s judgement need to be disclosed by virtue of their size, nature or incidence (termed ‘specific items’). Specific items are used to derive the adjusted results as presented in the accompanying consolidated income statement. Adjusted results are consistent with the way that financial performance is measured by management and assists in providing an additional analysis of the reporting trading results of the group. Specific items may not be comparable to similarly titled measures used by other companies. In determining whether an event or transaction is specific, management considers quantitative as well as qualitative factors. Examples of charges or credits meeting the above definition and which have been presented as specific items in the current and/or prior years include acquisitions/disposals of businesses and investments, retrospective regulatory matters, historical insurance or litigation claims, business restructuring programmes, asset impairment charges, property rationalisation programmes, net interest on pensions and the settlement of multiple tax years. In the event that other items meet the criteria, which are applied consistently from year to year, they are also treated as specific items. Half year 2018 £m 2017 £m Specific revenue Retrospective regulatory matters 36 14 Specific revenue 36 14 Specific operating costs Restructuring charge 206 130 Retrospective regulatory matters 5 13 Italian business investigation 1 6 EE acquisition warranty claims - 225 Profit on disposal of business - (1) Specific operating costs 212 373 Specific operating loss 248 387 Net interest expense on pensions 69 109 Net specific items charge before tax 317 496 Tax credit on specific items before tax (52) (46) Net specific items charge after tax 265 450 Restructuring charge During the first half of the year we incurred charges of £206m (H1 2017/18: £130m), primarily relating to leaver costs. These costs reflect projects within our group-wide cost transformation programme, including those costs related to the integration of EE. Retrospective regulatory matters We’ve recognised a net charge of £41m (H1 2017/18: £27m) in relation to regulatory matters in the first half of this year. This reflects the completion of the majority of compensation payments to other communications providers in relation to Ofcom’s March 2017 findings of its investigation into our historical practices on Deemed Consent by Openreach, and new matters arising. Of this, £36m is recognised in revenue and £5m in operating costs. Italian business investigation During the first half of the year we have incurred professional costs relating to the investigation of our Italian business of £1m (H1 2017/18: £6m). Interest expense on retirement benefit obligation During the first half of the year we incurred £69m (H1 2017/18: £109m) of interest costs in relation to our defined benefit pension obligations. Tax on specific items A tax credit of £52m (H1 2017/18: £46m) was recognised in relation to specific items. EE acquisition warranty claims In the prior year we reached settlements with Deutsche Telekom and Orange in respect of any warranty claims under the 2015 EE acquisition agreement, arising from the issues previously announced regarding our operations in Italy. This represents a full and final settlement of these issues and results in a specific item charge of £225m.

Pensions

Pensions	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Pensions	7 Pensions 30 September 2018 31 March 2018 (restated) £bn £bn IAS 19 liabilities – BTPS (55.6 ) (56.2 ) Assets – BTPS 50.8 49.9 Other schemes (0.5 ) (0.5 ) Total IAS 19 deficit, gross of tax (5.3 ) (6.8 ) Total IAS 19 deficit, net of tax (4.5 ) (5.7 ) Discount rate (nominal) 2.85 % 2.65 % Discount rate (real) (0.39 )% (0.44 )% RPI inflation 3.25 % 3.10 % CPI inflation 1.0% below RPI until 1.0% below RPI until

Financial instruments and risk

Financial instruments and risk management	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Financial instruments and risk management	8 Financial instruments and risk management Fair value of financial assets and liabilities measured at amortised cost At 30 September 2018, the fair value of listed bonds and other long-term borrowings was £17,507m (31 March 2018: £14,878m) and the carrying value was £16,212m (31 March 2018: £13,491m) and fair value of finance leases was £245m (31 March 2018: £253m) and carrying value was £218m (31 March 2018: £223m) The fair value of the following financial assets and liabilities approximate to their carrying amount: • Cash and cash equivalents • Trade and other receivables • Trade and other payables • Provisions • Investments held at amortised cost • Other short term borrowings • Investments classified as loans and receivable • Contract assets • Contract liabilities The group’s activities expose it to a variety of financial risks: market risk (including interest rate risk and foreign exchange risk); credit risk; and liquidity risk. There have been no changes to the risk management policies which cover these risks since 31 March 2018. Fair value estimation IFRS9 introduces three new categories of financial assets, fair value through profit and loss, fair value through other comprehensive income and amortised cost. At 31 March 2018 assets held at fair value included £2,575m of investments in liquidity funds, held as available for sale. These investments are held with the objective of collecting contractual cashflows. Under IFRS 9 they have therefore been classified as amortised cost. All other assets which were previously held as available for sale are now held as fair value through other comprehensive income. These instruments are further analysed by three levels of valuation methodology which are: 1. Level 1 – uses quoted prices in active markets for identical assets or liabilities 2. Level 2 – uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly 3. Level 3 – uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods. The fair value of the group’s outstanding derivative financial assets and liabilities were estimated using discounted cash flow models and market rates of interest and foreign exchange at the balance sheet date. Level 1 Level 2 Level 3 Total held at fair 30 September 2018 £m £m £m £m Investments Fair value through other comprehensive income 38 - 15 53 Fair value through profit and loss 6 - - 6 Derivative assets Designated in a hedge - 1,521 - 1,521 Fair value through profit and loss - 257 - 257 Total assets 44 1,778 15 1,837 Derivative liabilities Designated in a hedge - 564 - 564 Fair value through profit and loss - 195 - 195 Total liabilities - 759 - 759 Level 1 Level 2 Level 3 Total held at fair 31 March 2018 £m £m £m £m Investments Available for sale 32 2,575 14 2,621 Fair value through profit and loss 7 - - 7 Derivative assets Designated in a hedge - 1,248 - 1,248 Fair value through profit and loss - 261 - 261 Total assets 39 4,084 14 4,137 Derivative liabilities Designated in a hedge - 628 - 628 Fair value through profit and loss - 209 - 209 Total liabilities - 837 - 837 No gains or losses have been recognised in the income statement in respect of Level 3 assets held at 30 September 2018. There were no changes to the valuation methods or transfers between levels 1, 2 and 3 during the half year.

Financial commitments

Financial commitments	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Financial commitments	9 Financial commitments Capital expenditure for property, plant and equipment and software contracted for at the balance sheet date but not yet incurred was £1,293m (30 September 2017: £875m; 31 March 2018: £993m). Programme rights commitments, mainly relating to football broadcast rights for which the licence period has not yet started, were £2,866m (30 September 2017: £1,955m; 31 March 2018: £2,823m).

Contingent liabilities

Contingent liabilities	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Contingent liabilities	10 Contingent liabilities Save for the updates provided below, there have been no material updates relating to the Legal Proceedings and Regulatory matters as disclosed in the Annual Report 2018. Italian business – US securities class action complaints On 1 August 2018 our motion to dismiss the first amended complaint filed in the District of New Jersey in November 2017 was granted, without prejudice to the filing of a second amended complaint which was filed on 1 October 2018. On 29 October 2018 we filed our motion to dismiss this second amended complaint.

Post balance sheet events

Post balance sheet events	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Post balance sheet events	11 Post balance sheet events Changes in our segments From 1 October 2018, our existing Business and Public Sector and Wholesale and Ventures divisions will be brought together into a combined division, Enterprise, to accelerate transformation, simplify our operating model and strengthen accountabilities. These businesses operated and were reported separately throughout the first half of the 2018/19 financial year and therefore have been presented as separate operating segments throughout these accounts. In the first half of the year there were £10m of internal revenue and costs between Business and Public Sector and Wholesale and Ventures. Following our commitment to Ofcom in 2017 BT Group has completed the transfer of 31,000 employees to Openreach Limited from 1 October 2018, marking the final step in the creation of a more independent, legally separate business within the BT Group. As part of this, BT Northern Ireland Networks was renamed Openreach Northern Ireland and will be reported as part of Openreach (previously Business and Public Sector (Enterprise)). There is no impact on total group results, balance sheet or cash flows. BT’s pension schemes On 26 October, the High Court handed down a judgment involving the Lloyds Banking Group’s defined benefit pension schemes. The judgment concluded the schemes should be amended to equalise pension benefits for men and women in relation to guaranteed minimum pension benefits. The issues determined by the judgment arise in relation to many other defined benefit pension schemes. We are working with the trustees of our pension schemes, and our actuarial and legal advisers, to understand the extent to which the judgment crystallises additional liabilities for BT’s pension schemes. We estimate this could be in the hundreds of millions of pounds, and any adjustment necessary is expected to be recognised in the second half of 2018/19.

Related party transactions

Related party transactions	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Related party transactions	12 Related party transactions British Telecommunications plc and certain of its subsidiaries act as a funder and deposit taker for cash related transactions for both its parent (BT Group Investments Limited) and ultimate parent company (BT Group plc). The loan arrangements described below with these companies reflect this. Cash transactions normally arise where the parent and ultimate parent company are required to meet their external payment obligations or receive amounts from third parties. These principally relate to the payment of dividends, the buyback of shares and the exercise of share options. Transactions between the ultimate parent company, the parent company and the group are settled on both a cash and non-cash In 2001/02 the group demerged its former mobile phone business and as a result BT Group plc became the listed ultimate parent company of the group. The demerger steps resulted in the formation of an intermediary holding company, BT Group Investments Limited, between BT Group plc and British Telecommunications plc. This intermediary company held an investment of £18.5bn in British Telecommunications plc which was funded by an intercompany loan facility with British Telecommunications plc. A dividend BT plc of £2,500m (2017: £nil) was declared and settled with the parent company in relation to the year ended 31 March 2018 during the first half. A summary of the balances with the parent and ultimate parent companies and the finance income or expense arising in respect of these balances is shown below: Asset (liability) Finance income (expense) 30 September 31 March 30 September 30 September £m £m £m £m Amounts owed by (to) parent company Loan facility – non-current 10,486 10,318 105 84 Loan facility – current asset investments 105 168 n/a n/a Trade and other payables (73 ) (50 ) n/a n/a Amounts owed by (to) ultimate parent company Non-current 3,024 2,983 30 13 Non-current (1,061 ) (1,044 ) (22 ) (9 ) Trade and other receivables 16 15 n/a n/a Current asset investments 30 34 n/a n/a Current liabilities (1,477 ) (18 ) n/a n/a

Principal risks and uncertainti

Principal risks and uncertainties	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Principal risks and uncertainties	13 Principal risks and uncertainties We have processes for identifying, evaluating and managing our risks. Details of our principal risks and uncertainties can be found on pages 34 to 47 of the Annual Report 2018 and are summarised below. All of them have the potential to have an adverse impact on our business, revenue, profits, assets, liquidity and capital resources. • The risks associated with operating under a wide range of local and international laws, trade sanctions and import and export controls; coupled with the risk of inappropriate and unethical behaviour by our people or associates • The risks arising from operating as a major data controller and processor of customer information around the world • The risks arising from our operational activities, and in particular the work of our engineers, that are subject to health and safety regulation and enforcement by national authorities. This also extends to the risks associated with the transmission of radio waves from mobile telephones, transmitters and associated equipment – although according to the World Health Organisation there are no known adverse effects on health from emissions at levels below internationally recognised health and safety standards • The risks arising from operating in markets which are characterised by: high levels of change; strong and new competition; declining prices and in some markets declining revenue; technology substitution; market and product convergence; customer churn; and regulatory intervention to promote competition and reduce wholesale prices • The risks associated with some of our activities being subject to significant price and other regulatory controls • The risks associated with a significant funding obligation in relation to our defined benefit pension schemes, and in particular the BT Pension Scheme • The risks associated with political and geopolitical trends and incidents, including the uncertainty caused by the UK voting to leave the European Union • The financial risks common to other major international businesses, including market, credit, liquidity and tax risks • The risks that could impact the security of our data or the resilience of our operations and services • The risks associated with complex and high value national and multinational customer contracts • The risk there could be a failure of any of our critical third-party suppliers to meet their obligations • The risks associated with not being able to secure sufficient employee engagement to support delivery of our strategic aims There have been no significant changes to the principal risks and uncertainties in the half year to 30 September 2018. These principal risks and uncertainties continue to have the potential to impact our results or financial position during the remaining six months of the financial year.

Basis of preparation and acco_2

Basis of preparation and accounting policies (Policies)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
IFRS 15 'Revenue from contracts with customers'	IFRS 15 ‘Revenue from contracts with customers’ Background IFRS 15 sets out the requirements for recognising revenue and costs from contracts with customers and includes extensive disclosure requirements. The standard requires entities to apportion revenue earned from contracts to individual performance obligations, on a relative stand-alone selling price basis, based on a five-step model. As disclosed in our Annual Report 2018 we have adopted the standard on a modified retrospective basis and have recognised the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings at 1 April 2018. Under this transition method: – the standard has been applied only to contracts in progress but not completed at the date of initial application; – for contracts that were modified before 1 April 2018, we have reflected the aggregate effect of all of the modifications that occur before this date at 1 April 2018; – we have not restated prior year comparatives for the effect of IFRS 15 but have instead restated our 1 April 2018 opening retained earnings for the full cumulative impact of adopting this standard; and – for the year ended 31 March 2019 we will provide a reconciliation of our primary financial statements under IFRS 15 to those in accordance with IAS 18 in our Annual Report & Form 20-F Financial impact In our Annual Report 2018 we estimated that the likely impact on transition at 1 April 2018 would produce a cumulative increase in retained earnings of between £1.1bn and £1.5bn before tax. The actual increase of £1.3bn before tax (£1.1bn after tax) has primarily been recorded as a contract asset and will lead to an additional one-off cash tax payment of £0.2bn equally split between 2018/19 and 2019/20. The cumulative increase in retained earnings is mainly due to the acceleration of handset revenues and, to a lesser extent, deferral of costs (notably third party contract acquisition costs primarily associated with post pay mobile contracts). The financial impact of each business area is as follows: – Under our previous accounting policy, mobile handset revenue was recognised based on the amount the customer pays for the handset when it is delivered to the customer. Generally mobile handsets are either provided free or for a small upfront charge. Under IFRS 15, additional revenue is allocated to the mobile handset at the start of the contract. This is calculated with reference to its relative standalone value within the contract, regardless of the contract pricing. For each mobile handset contract the revenue recognition profile changed with greater day one recognition of revenue for the handset and a corresponding reduction in ongoing mobile service revenue over the contract period. The difference between the mobile handset revenue recognised and the amounts charged to the customer has been recognised as a contract asset. Over time, we expect the contract asset generated to remain at similar levels as old contracts expire and new ones are signed. However, we will see short-term volatility, for example around key handset launches. This primarily impacted Consumer, and to a lesser extent this also impacted mobile handset revenues in Business and Public Sector in respect of the legacy EE business division. We saw a similar trend in respect of subsidised equipment although this had a less significant impact due to the lower relative standalone value for this equipment. – Previously, sales commissions and other third party acquisition costs resulting directly from securing contracts with customers were expensed when incurred. Under IFRS 15 sales commissions and other third party contract acquisition costs are recognised as an asset, and amortised over the period in which the corresponding benefit is received, resulting in earlier profit recognition. The impact is greatest in Consumer in respect of third-party acquisition costs. – The above two impacts are partly offset by amended accounting for connections revenue. Previously, the group recognised connections revenue upon performance of the connection activity. Under IFRS 15 connections revenue is deferred and recognised on a straight-line basis over the associated line/circuit contractual period. This means that revenue and profits are recognised later. On transition this led to the recognition of a contract liability as revenue and profits are deferred to future periods. Wholesale and Ventures and Openreach deliver the majority of this service and therefore experienced the majority of the impact. Over time, this liability is expected to remain at similar levels as old contracts expire and new ones are signed. – The IFRS 15 impact on other areas was not material. This included certain contract fulfilment costs which are recognised as an asset and amortised over the period in which benefit is received and certain expenses are recognised as a deduction from revenue.
Pro forma	Pro forma We have prepared and published unaudited pro forma results for the years ended 31 March 2018 and 31 March 2017 under IFRS 15. While BT believes the pro forma information contained in this document to be reliable, BT does not warrant the accuracy, completeness or validity of the information, figures or calculations and shall not be liable in any way for loss or damage arising out of the use of the information, or any errors or omissions in its content.
IFRS 9 'Financial Instruments'	IFRS 9 ‘Financial Instruments’ IFRS 9 is applicable to financial assets and financial liabilities and covers the classification, measurement, impairment and de- There are no other new or amended standards or interpretations adopted during the year that have a significant impact on the group. New and amended accounting standards that have been issued but are not yet effective
IFRS 16 'Leases'	IFRS 16 ‘Leases’ We will report our financial statements under IFRS 16 from the first quarter of 2019/20. We expect to adopt IFRS 16 on a modified retrospective basis in our 2019/20 financial statements. Accordingly we will not restate prior year comparatives for the effect of IFRS 16 but will instead restate our 1 April 2019 opening reserves for the full cumulative impact of adopting this standard. The standard requires lessees to recognise assets and liabilities for all leases unless the lease term is 12 months or less, or the underlying asset is of low value. We are still in the process of quantifying the implications of this standard. However, we expect the following indicative impacts: – there is expected to be an increase in total assets, as leased assets which are currently accounted for off balance sheet (i.e. classified as operating leases under IAS 17) will be recognised on balance sheet and valued in accordance with the principles of IFRS 16. The biggest asset category impacted for the group is expected to be land and buildings – there is expected to be an increase in debt, as liabilities relating to existing operating leases are recognised – operating lease expenditure will be reclassified and split between depreciation and finance costs. Therefore EBITDA will increase. Future depreciation and finance costs are also expected to increase as a result of increased assets and liabilities – there is an expected temporary reduction in profit after tax. This is expected to be driven by an increase in finance costs as a result of the new leases. These finance costs will have an accelerated profile which will reduce over the lease term – there may be a corresponding effect on tax balances in relation to all of the above impacts. This standard will require us to make key accounting judgements in particular around the likelihood of lease renewals. Details of our existing operating lease commitments at 31 March 2018 are set out in note 30 of our Annual Report 2018.

Restatement of prior period f_2

Restatement of prior period financial statements (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Opening Balance Adjustment of IFRS 15 and IFRS 9	The impact of the retirement benefit obligation restatement and the IFRS 15 and IFRS 9 opening balance adjustment have been set out in the reconciliations below: Group statement of comprehensive income Year to 31 March 2018 As published Pensions Restated Profit for the period 2,184 - 2,184 Other comprehensive income (loss) Items that will not be reclassified to the income statement: Remeasurements of the net pension obligation 2,160 (476 ) 1,684 Tax on pension remeasurements (346 ) 83 (263 ) Items that have been or may be reclassified subsequently to the income statement: Exchange differences on translation of foreign operations (188 ) - (188 ) Fair value movements on available-for-sale 11 - 11 Fair value movements on cash flow hedges: - net fair value (losses) gains (368 ) - (368 ) - recognised in income and expense 277 - 277 Movement on cost of hedging reserve - - - Tax on components of other comprehensive income that have been or may be reclassified 1 - 1 Other comprehensive profit (loss) for the period, net of tax 1,547 (393 ) 1,154 Total comprehensive income (loss) for the period 3,731 (393 ) 3,338 Group balance sheet At 31 March as published Pension At 31 March 2018 restated IFRS 1 At 1 April £m £m £m £m £m Non-current Intangible assets 14,455 - 14,455 - 14,455 Property, plant and equipment 17,000 - 17,000 - 17,000 Investments 13,354 - 13,354 - 13,354 Trade and other receivables 317 - 317 114 431 Contract assets - - - 198 198 Deferred tax assets 1,243 83 1,326 - 1,326 Other non-current 1,350 1,350 - 1,350 47,719 83 47,802 312 48,114 Current assets Trade and other receivables 4,029 - 4,029 (337) 3,692 Contract assets - - - 1,417 1,417 Cash and cash equivalents 521 - 521 - 521 Other current assets 4,009 - 4,009 - 4,009 8,559 - 8,559 1,080 9,639 Current liabilities Loans and other borrowings 2,298 - 2,298 - 2,298 Trade and other payables 7,190 - 7,190 (1,409) 5,781 Contract liabilities - - - 1,406 1,406 Current tax liabilities 83 - 83 248 331 Other current liabilities 653 - 653 - 653 10,224 - 10,224 245 10,469 Total assets less current liabilities 46,054 83 46,137 1,147 47,284 Non-current Loans and other borrowings 13,038 - 13,038 - 13,038 Retirement benefit obligations 6,371 476 6,847 - 6,847 Other non-current 3,905 - 3,905 87 3,992 23,314 476 23,790 87 23,877 Equity Share capital 2,172 - 2,172 - 2,172 Share premium 8,000 - 8,000 - 8,000 All other reserves 1,241 - 1,241 - 1,241 Retained earnings 11,327 (393) 10,934 1,060 11,994 Total equity 22,740 (393) 22,347 1,060 23,407 46,054 83 46,137 1,147 47,284 Group statement of changes in equity Share Share Other Retained Total £m £m £m £m £m At 31 March 2018 - as published 2,172 8,000 1,241 11,327 22,740 Pension restatement - - - (393) (393) At 31 March 2018 – restated 2,172 8,000 1,241 10,934 22,347 IFRS opening balance adjustment 1 - - - 1,308 1,308 Tax on IFRS opening balance adjustment 1 - - - (248) (248) At 1 April 2018 2,172 8,000 1,241 11,994 23,407 1 This reflects the opening balance sheet adjustment for both IFRS 15 and IFRS 9. See note 1 to the condensed consolidated financial statements

Operating results - by custom_2

Operating results - by customer facing unit (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Operating Results by Customer Facing Unit	External Internal Group EBITDA 1 Operating Half year to 30 September 2018 (IFRS 15 basis) £m £m £m £m £m Consumer 5,220 52 5,272 1,221 713 Business and Public Sector 2 2,140 55 2,195 708 529 Wholesale and Ventures 2 873 56 929 325 173 Global Services 2,332 - 2,332 208 22 Openreach 1,057 1,415 2,472 1,177 498 Other 2 - 2 37 5 Intra-group items - (1,578 ) (1,578 ) - - Total adjusted 3 11,624 - 11,624 3,676 1,940 Specific items (note 6) (36 ) (248 ) Total 11,588 1,692 Half year to 30 September 2017 (IAS 18 basis) Consumer (restated) 4 5,083 50 5,133 1,139 654 Business and Public Sector 2,224 57 2,281 694 509 Wholesale and Ventures 926 71 997 361 207 Global Services 2,506 - 2,506 154 (67 ) Openreach 1,054 1,494 2,548 1,238 548 Other 7 - 7 12 (10 ) Intra-group items - (1,672 ) (1,672 ) - - Total adjusted 3 11,800 - 11,800 3,598 1,841 Specific items (note 6) (14 ) (387 ) Total 11,786 1,454 1 2 3 4

Operating result - by type of_2

Operating result - by type of revenue (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Operating Result by Type of Revenue	Half year to 30 September 2018 2017 £m £m ICT and managed networks 2,203 2,256 Fixed access subscription revenue 4,641 4,814 Mobile subscription revenue 2,659 3,086 Equipment and other services 2,121 1,644 Total adjusted 2 11,624 11,800 Specific items (note 6) (36) (14) Total 11,588 11,786 1 re-presented 2

Operating costs (Tables)

Operating costs (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Operating Costs	Half year 2018 (IFRS 15) 2017 (IAS 18) £m £m Direct labour costs 2,663 2,688 Indirect labour costs 472 451 Leaver costs 8 30 Total labour costs 3,143 3,169 Capitalised labour (729 ) (668 ) Net labour costs 2,414 2,501 Product costs and sales commissions 1 2,172 2,153 Payments to telecommunications operators 1,073 1,207 Property and energy costs 661 649 Network operating and IT costs 508 476 Programme rights charges 403 377 Other operating costs 1 717 839 Operating costs before depreciation, amortisation and specific items 7,948 8,202 Depreciation and amortisation 1,736 1,757 Total operating costs before specific items 9,684 9,959 Specific items (Note 6) 212 373 Total operating costs 9,896 10,332 1 Other operating costs have been disaggregated and re-presented

Specific items (Tables)

Specific items (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Specific Items	Half year 2018 £m 2017 £m Specific revenue Retrospective regulatory matters 36 14 Specific revenue 36 14 Specific operating costs Restructuring charge 206 130 Retrospective regulatory matters 5 13 Italian business investigation 1 6 EE acquisition warranty claims - 225 Profit on disposal of business - (1) Specific operating costs 212 373 Specific operating loss 248 387 Net interest expense on pensions 69 109 Net specific items charge before tax 317 496 Tax credit on specific items before tax (52) (46) Net specific items charge after tax 265 450

Pensions (Tables)

Pensions (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Pensions	30 September 2018 31 March 2018 (restated) £bn £bn IAS 19 liabilities – BTPS (55.6 ) (56.2 ) Assets – BTPS 50.8 49.9 Other schemes (0.5 ) (0.5 ) Total IAS 19 deficit, gross of tax (5.3 ) (6.8 ) Total IAS 19 deficit, net of tax (4.5 ) (5.7 ) Discount rate (nominal) 2.85 % 2.65 % Discount rate (real) (0.39 )% (0.44 )% RPI inflation 3.25 % 3.10 % CPI inflation 1.0% below RPI until 1.0% below RPI until

Financial instruments and ris_2

Financial instruments and risk management (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Summary of Fair Value of Derivative Financial Assets and Liabilities Estimated Using Discounted Cash Flow Models, Market Rates and Foreign Exchange	The fair value of the group’s outstanding derivative financial assets and liabilities were estimated using discounted cash flow models and market rates of interest and foreign exchange at the balance sheet date. Level 1 Level 2 Level 3 Total held at fair 30 September 2018 £m £m £m £m Investments Fair value through other comprehensive income 38 - 15 53 Fair value through profit and loss 6 - - 6 Derivative assets Designated in a hedge - 1,521 - 1,521 Fair value through profit and loss - 257 - 257 Total assets 44 1,778 15 1,837 Derivative liabilities Designated in a hedge - 564 - 564 Fair value through profit and loss - 195 - 195 Total liabilities - 759 - 759 Level 1 Level 2 Level 3 Total held at fair 31 March 2018 £m £m £m £m Investments Available for sale 32 2,575 14 2,621 Fair value through profit and loss 7 - - 7 Derivative assets Designated in a hedge - 1,248 - 1,248 Fair value through profit and loss - 261 - 261 Total assets 39 4,084 14 4,137 Derivative liabilities Designated in a hedge - 628 - 628 Fair value through profit and loss - 209 - 209 Total liabilities - 837 - 837

Related party transactions (Tab

Related party transactions (Tables)	6 Months Ended
	Sep. 30, 2018
Text block1 [abstract]
Balances with Parent and Ultimate Parent Companies and Finance Income or Expense	A summary of the balances with the parent and ultimate parent companies and the finance income or expense arising in respect of these balances is shown below: Asset (liability) Finance income (expense) 30 September 31 March 30 September 30 September £m £m £m £m Amounts owed by (to) parent company Loan facility – non-current 10,486 10,318 105 84 Loan facility – current asset investments 105 168 n/a n/a Trade and other payables (73 ) (50 ) n/a n/a Amounts owed by (to) ultimate parent company Non-current 3,024 2,983 30 13 Non-current (1,061 ) (1,044 ) (22 ) (9 ) Trade and other receivables 16 15 n/a n/a Current asset investments 30 34 n/a n/a Current liabilities (1,477 ) (18 ) n/a n/a

Basis of Preparation and Acco_3

Basis of Preparation and Accounting Policies - Additional Information (Detail) - GBP (£)	Apr. 01, 2018	Sep. 30, 2018
Disclosure of basis of preparation and summary of significant accounting policies [line items]
Cash tax payment		£ 200,000,000
Retained earnings [member] | Bottom of range [member]
Disclosure of basis of preparation and summary of significant accounting policies [line items]
Cumulative increase in retained earnings	£ 1,100,000,000
Retained earnings [member] | Top of range [member]
Disclosure of basis of preparation and summary of significant accounting policies [line items]
Cumulative increase in retained earnings	1,500,000,000
Contract assets [member] | Before tax [member] | Retained earnings [member]
Disclosure of basis of preparation and summary of significant accounting policies [line items]
Cumulative increase in retained earnings	1,300,000,000
Contract assets [member] | After tax [member] | Retained earnings [member]
Disclosure of basis of preparation and summary of significant accounting policies [line items]
Cumulative increase in retained earnings	£ 1,100,000,000

Restatement of Prior Period F_3

Restatement of Prior Period Financial Statements - Additional Information (Detail) - GBP (£) £ in Millions	6 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018		Apr. 01, 2018	Mar. 31, 2017
Disclosure Of Restatement [Line Items]
Total equity	£ 21,999	£ 19,772	£ 22,347	[1]	£ 23,407	£ 18,926
Remeasurements of the net pension obligation	(292)	(4)
Tax expense on pension re-measurement	£ 58	£ 17
Increase (decrease) due to corrections of prior period errors [member]
Disclosure Of Restatement [Line Items]
Increase in retirement benefit obligation, after tax			393
Increase in retirement benefit obligation, gross			476
Total equity			393
Remeasurements of the net pension obligation			476
Tax expense on pension re-measurement			£ 83
[1]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements

Restatement of prior period f_4

Restatement of prior period financial statements - Summary of Opening Balance Adjustment of IFRS 15 and IFRS 9 - Statement of Comprehensive Income (Detail) - GBP (£) £ in Millions	6 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Disclosure Of Restatement [Line Items]
Profit for the period	£ 1,144	£ 881
Other comprehensive income (loss)	(91)	(78)
Items that will not be reclassified to the income statement:
Remeasurements of the net pension obligation	(292)	(4)
Tax on pension remeasurements	(58)	(17)
Items that have been or may be reclassified subsequently to the income statement:
Exchange differences on translation of foreign operations	74	(115)
Fair value movements on available-for-sale assets	5	4
Fair value movements on cash flow hedges:
- net fair value (losses) gains	477	(49)
- recognised in income and expense	(293)	78
Movement on cost of hedging reserve	(90)
Tax on components of other comprehensive income that have been or may be reclassified	30	9
Other comprehensive profit (loss) for the period, net of tax	(91)	(78)
Total comprehensive income (loss) for the period	£ 1,053	£ 803
Previously reported [member]
Disclosure Of Restatement [Line Items]
Profit for the period			£ 2,184
Other comprehensive income (loss)			1,547
Items that will not be reclassified to the income statement:
Remeasurements of the net pension obligation			2,160
Tax on pension remeasurements			(346)
Items that have been or may be reclassified subsequently to the income statement:
Exchange differences on translation of foreign operations			(188)
Fair value movements on available-for-sale assets			11
Fair value movements on cash flow hedges:
- net fair value (losses) gains			(368)
- recognised in income and expense			277
Movement on cost of hedging reserve			0
Tax on components of other comprehensive income that have been or may be reclassified			1
Other comprehensive profit (loss) for the period, net of tax			1,547
Total comprehensive income (loss) for the period			3,731
Pension adjustments [member]
Disclosure Of Restatement [Line Items]
Other comprehensive income (loss)			(393)
Items that will not be reclassified to the income statement:
Remeasurements of the net pension obligation			(476)
Tax on pension remeasurements			83
Fair value movements on cash flow hedges:
Movement on cost of hedging reserve			0
Other comprehensive profit (loss) for the period, net of tax			(393)
Total comprehensive income (loss) for the period			(393)
Restated [member]
Disclosure Of Restatement [Line Items]
Profit for the period			2,184
Other comprehensive income (loss)			1,154
Items that will not be reclassified to the income statement:
Remeasurements of the net pension obligation			1,684
Tax on pension remeasurements			(263)
Items that have been or may be reclassified subsequently to the income statement:
Exchange differences on translation of foreign operations			(188)
Fair value movements on available-for-sale assets			11
Fair value movements on cash flow hedges:
- net fair value (losses) gains			(368)
- recognised in income and expense			277
Movement on cost of hedging reserve			0
Tax on components of other comprehensive income that have been or may be reclassified			1
Other comprehensive profit (loss) for the period, net of tax			1,154
Total comprehensive income (loss) for the period			£ 3,338

Restatement of prior period f_5

Restatement of prior period financial statements - Summary of Opening Balance Adjustment of IFRS 15 and IFRS 9 - Group Balance Sheet (Detail) - GBP (£) £ in Millions	Sep. 30, 2018		Apr. 01, 2018	Mar. 31, 2018		Sep. 30, 2017	Mar. 31, 2017
Non-currentassets
Intangible assets	£ 14,618		£ 14,455	£ 14,455	[1]
Property, plant and equipment	17,234		17,000	17,000	[1]
Investments	13,569		13,354	13,354	[1]
Trade and other receivables	436		431	317	[1]
Contract assets	239	[2]	198
Deferred tax assets	1,003		1,326	1,326	[1]
Other non-current assets			1,350
Non current assets	48,609		48,114	47,802	[1]
Current assets
Trade and other receivables	3,570		3,692	4,029	[1]
Contract assets	1,321	[2]	1,417
Cash and cash equivalents	421		521	521	[1]
Other current assets			4,009
Current assets	10,314		9,639	8,559	[1]
Current liabilities
Loans and other borrowings	4,290		2,298	2,298	[1]
Trade and other payables	5,771		5,781	7,190	[1]
Contract liabilities	1,343	[2]	1,406
Current tax liabilities	211		331	83	[1]
Other current liabilities			653
Current liabilities	12,275		10,469	10,224	[1]
Total assets less current liabilities	46,648		47,284	46,137	[1]
Non-current liabilities
Loans and other borrowings	15,317		13,038	13,038	[1]
Retirement benefit obligations	5,280		6,847	6,847	[1]
Other non-current liabilities			3,992
Non current liabilities	24,649		23,877	23,790	[1]
Equity
Share capital	2,172		2,172	2,172	[1]
Share premium	8,000		8,000	8,000	[1]
All other reserves	1,384		1,241	1,241	[1]
Retained earnings	10,443		11,994	10,934	[1]
Total equity	21,999		23,407	22,347	[1]	£ 19,772	£ 18,926
Total equity and Liabilities	£ 46,648		£ 47,284	46,137	[1]
Previously reported [member]
Non-currentassets
Intangible assets				14,455
Property, plant and equipment				17,000
Investments				13,354
Trade and other receivables				317
Deferred tax assets				1,243
Other non-current assets				1,350
Non current assets				47,719
Current assets
Trade and other receivables				4,029
Cash and cash equivalents				521
Other current assets				4,009
Current assets				8,559
Current liabilities
Loans and other borrowings				2,298
Trade and other payables				7,190
Current tax liabilities				83
Other current liabilities				653
Current liabilities				10,224
Total assets less current liabilities				46,054
Non-current liabilities
Loans and other borrowings				13,038
Retirement benefit obligations				6,371
Other non-current liabilities				3,905
Non current liabilities				23,314
Equity
Share capital				2,172
Share premium				8,000
All other reserves				1,241
Retained earnings				11,327
Total equity				22,740
Total equity and Liabilities				46,054
Pension adjustments [member]
Non-currentassets
Deferred tax assets				83
Non current assets				83
Current liabilities
Total assets less current liabilities				83
Non-current liabilities
Retirement benefit obligations				476
Non current liabilities				476
Equity
Retained earnings				(393)
Total equity				(393)
Total equity and Liabilities				83
Restated [member]
Non-currentassets
Intangible assets				14,455
Property, plant and equipment				17,000
Investments				13,354
Trade and other receivables				317
Deferred tax assets				1,326
Other non-current assets				1,350
Non current assets				47,802
Current assets
Trade and other receivables				4,029
Cash and cash equivalents				521
Other current assets				4,009
Current assets				8,559
Current liabilities
Loans and other borrowings				2,298
Trade and other payables				7,190
Current tax liabilities				83
Other current liabilities				653
Current liabilities				10,224
Total assets less current liabilities				46,137
Non-current liabilities
Loans and other borrowings				13,038
Retirement benefit obligations				6,847
Other non-current liabilities				3,905
Non current liabilities				23,790
Equity
Share capital				2,172
Share premium				8,000
All other reserves				1,241
Retained earnings				10,934
Total equity				22,347
Total equity and Liabilities				46,137
IFRS Adjustment [member]
Non-currentassets
Trade and other receivables				114
Contract assets				198
Non current assets				312
Current assets
Trade and other receivables				(337)
Contract assets				1,417
Current assets				1,080
Current liabilities
Trade and other payables				(1,409)
Contract liabilities				1,406
Current tax liabilities				248
Current liabilities				245
Total assets less current liabilities				1,147
Non-current liabilities
Other non-current liabilities				87
Non current liabilities				87
Equity
Retained earnings				1,060
Total equity				1,060
Total equity and Liabilities				£ 1,147
[1]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements
[2]	Contract assets and contract liabilities arise following the adoption of IFRS 15 on 1 April 2018. See note 1 to the condensed consolidated financial statements.

Restatement of prior period f_6

Restatement of prior period financial statements - Summary of Opening Balance Adjustment of IFRS 15 and IFRS 9 - Statement of Changes in Equity (Detail) - GBP (£) £ in Millions		Apr. 01, 2018	Mar. 31, 2018
Disclosure Of Restatement [Line Items]
IFRS opening balance adjustment	[1]	£ 1,308
Beginning balance	[2]	22,347
Tax on IFRS opening balance adjustment	[1]	(248)
Ending balance		23,407	£ 22,347	[2]
Previously reported [member]
Disclosure Of Restatement [Line Items]
Beginning balance		22,740
Ending balance			22,740
Pension adjustments [member]
Disclosure Of Restatement [Line Items]
Beginning balance		(393)
Pension restatement	[3]		(393)
Ending balance			(393)
Restated [member]
Disclosure Of Restatement [Line Items]
Beginning balance		22,347
Ending balance			22,347
Share capital [member]
Disclosure Of Restatement [Line Items]
Ending balance		2,172
Share capital [member] | Previously reported [member]
Disclosure Of Restatement [Line Items]
Beginning balance		2,172
Ending balance			2,172
Share capital [member] | Restated [member]
Disclosure Of Restatement [Line Items]
Beginning balance		2,172
Ending balance			2,172
Share premium [member]
Disclosure Of Restatement [Line Items]
Ending balance		8,000
Share premium [member] | Previously reported [member]
Disclosure Of Restatement [Line Items]
Beginning balance		8,000
Ending balance			8,000
Share premium [member] | Restated [member]
Disclosure Of Restatement [Line Items]
Beginning balance		8,000
Ending balance			8,000
Other reserves [member]
Disclosure Of Restatement [Line Items]
Ending balance		1,241
Other reserves [member] | Previously reported [member]
Disclosure Of Restatement [Line Items]
Beginning balance		1,241
Ending balance			1,241
Other reserves [member] | Restated [member]
Disclosure Of Restatement [Line Items]
Beginning balance		1,241
Ending balance			1,241
Retained earnings [member]
Disclosure Of Restatement [Line Items]
IFRS opening balance adjustment		1,308
Tax on IFRS opening balance adjustment		(248)
Ending balance		11,994
Retained earnings [member] | Previously reported [member]
Disclosure Of Restatement [Line Items]
Beginning balance		11,327
Ending balance			11,327
Retained earnings [member] | Pension adjustments [member]
Disclosure Of Restatement [Line Items]
Pension restatement			(393)
Retained earnings [member] | Restated [member]
Disclosure Of Restatement [Line Items]
Beginning balance		£ 10,934
Ending balance			£ 10,934
[1]	See Note 1 to the condensed consolidated financial statements
[2]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements
[3]	See Note 2 to the condensed consolidated financial statements

Operating Results - by Custom_3

Operating Results - by Customer Facing Unit - Summary of Operating Results by Customer Facing Unit (Detail) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of operating segments [line items]
Group revenue	£ 11,588	£ 11,786
Operating profit	1,692	1,454
Adjusted [member]
Disclosure of operating segments [line items]
Group revenue	11,624	11,800
EBITDA	3,676	3,598
Operating profit	1,940	1,841
Specific items [member]
Disclosure of operating segments [line items]
Group revenue	(36)	(14)
Operating profit	(248)	(387)
Consumer [member]
Disclosure of operating segments [line items]
Group revenue	5,272	5,133
EBITDA	1,221	1,139
Operating profit	713	654
Business and public sector [member]
Disclosure of operating segments [line items]
Group revenue	2,195	2,281
EBITDA	708	694
Operating profit	529	509
Wholesale and ventures [member]
Disclosure of operating segments [line items]
Group revenue	929	997
EBITDA	325	361
Operating profit	173	207
Global services [member]
Disclosure of operating segments [line items]
Group revenue	2,332	2,506
EBITDA	208	154
Operating profit	22	(67)
Openreach [member]
Disclosure of operating segments [line items]
Group revenue	2,472	2,548
EBITDA	1,177	1,238
Operating profit	498	548
Other [member]
Disclosure of operating segments [line items]
Group revenue	2	7
EBITDA	37	12
Operating profit	5	(10)
Elimination of intersegment amounts [member]
Disclosure of operating segments [line items]
Group revenue	(1,578)	(1,672)
External revenue [member] | Adjusted [member]
Disclosure of operating segments [line items]
Group revenue	11,624	11,800
External revenue [member] | Consumer [member]
Disclosure of operating segments [line items]
Group revenue	5,220	5,083
External revenue [member] | Business and public sector [member]
Disclosure of operating segments [line items]
Group revenue	2,140	2,224
External revenue [member] | Wholesale and ventures [member]
Disclosure of operating segments [line items]
Group revenue	873	926
External revenue [member] | Global services [member]
Disclosure of operating segments [line items]
Group revenue	2,332	2,506
External revenue [member] | Openreach [member]
Disclosure of operating segments [line items]
Group revenue	1,057	1,054
External revenue [member] | Other [member]
Disclosure of operating segments [line items]
Group revenue	2	7
Internal revenue [member] | Consumer [member]
Disclosure of operating segments [line items]
Group revenue	52	50
Internal revenue [member] | Business and public sector [member]
Disclosure of operating segments [line items]
Group revenue	55	57
Internal revenue [member] | Wholesale and ventures [member]
Disclosure of operating segments [line items]
Group revenue	56	71
Internal revenue [member] | Openreach [member]
Disclosure of operating segments [line items]
Group revenue	1,415	1,494
Internal revenue [member] | Elimination of intersegment amounts [member]
Disclosure of operating segments [line items]
Group revenue	£ (1,578)	£ (1,672)

Operating Result - by Type of_3

Operating Result - by Type of Revenue - Summary of Operating Result by Type of Revenue (Detail) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of products and services [line items]
Operating result - by type of revenue	£ 11,588	£ 11,786
Adjusted [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	11,624	11,800
Specific items [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	(36)	(14)
ICT and managed networks [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	2,203	2,256
Fixed access subscription revenue [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	4,641	4,814
Mobile subscription revenue [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	2,659	3,086
Equipment and other services [member]
Disclosure of products and services [line items]
Operating result - by type of revenue	£ 2,121	£ 1,644

Operating Costs - Summary of Op

Operating Costs - Summary of Operating Costs (Detail) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of operating costs [line items]
Direct labour costs	£ 2,663	£ 2,688
Indirect labour costs	472	451
Leaver costs	8	30
Total labour costs	3,143	3,169
Capitalised labour	(729)	(668)
Net labour costs	2,414	2,501
Product costs and sales commissions	2,172	2,153
Payments to telecommunications operators	1,073	1,207
Property and energy costs	661	649
Network operating and IT costs	508	476
Programme rights charges	403	377
Other operating costs	717	839
Operating costs before depreciation, amortisation and specific items	7,948	8,202
Depreciation and amortisation	1,736	1,757
Total operating costs	9,896	10,332
Before Specific Items [member]
Disclosure of operating costs [line items]
Total operating costs	9,684	9,959
Specific items [member]
Disclosure of operating costs [line items]
Total operating costs	£ 212	£ 373

Specific Items - Summary of Spe

Specific Items - Summary of Specific Items (Detail) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Specific revenue
Specific revenue	£ 11,588	£ 11,786
Specific operating costs
Specific operating costs	(9,896)	(10,332)
Specific operating loss	(1,692)	(1,454)
Profit before tax	(1,454)	(1,174)
Net specific items charge after tax	(1,144)	(881)
Specific items [member]
Specific revenue
Retrospective regulatory matters	36	14
Specific revenue	36	14
Specific operating costs
Restructuring charge	206	130
Retrospective regulatory matters	5	13
Italian business investigation	1	6
EE acquisition warranty claims		225
Profit on disposal of business		(1)
Specific operating costs	212	373
Specific operating loss	248	387
Net interest expense on pensions	69	109
Profit before tax	317	496
Tax credit on specific items before tax	(52)	(46)
Net specific items charge after tax	£ 265	£ 450

Specific Items - Additional Inf

Specific Items - Additional Information (Detail) - Specific items [member] - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure of specific items [line items]
Restructuring charges	£ 206	£ 130
Regulatory matters effect	41	27
Regulatory matters revenue	36
Regulatory costs recognised as specific items	5
Investigation of Italian business	1	6
Interest expense on retirement benefit obligation	69	109
Tax credit on specific items	52	46
EE acquisition warranty claim		£ 225
Deutsche Telekom and Orange [Member]
Disclosure of specific items [line items]
EE acquisition warranty claim	£ 225

Pensions -Summary of Pensions (

Pensions -Summary of Pensions (Detail) - GBP (£) £ in Billions	6 Months Ended	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018
Disclosure of net defined benefit liability (asset) [line items]
Other schemes	£ (0.5)	£ (0.5)
Total IAS 19 deficit, gross of tax	(5.3)	(6.8)
Total IAS 19 deficit, net of tax	£ (4.5)	£ (5.7)
Discount rate (nominal)	2.85%	2.65%
Discount rate (real)	(0.39%)	(0.44%)
RPI inflation	3.25%	3.10%
CPI inflation	1.0% below RPI until 31 March 2023 and 1.1% below RPI thereafter	1.0% below RPI until 31 March 2023 and 1.1% below RPI thereafter
BTPS [member]
Disclosure of net defined benefit liability (asset) [line items]
IAS 19 liabilities - BTPS	£ (55.6)	£ (56.2)
Assets - BTPS	£ 50.8	£ 49.9

Financial instruments and ris_3

Financial instruments and risk management - Additional Information (Detail) - GBP (£)	6 Months Ended
	Sep. 30, 2018	Mar. 31, 2018
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Fair value of financial liabilities	£ 759,000,000	£ 837,000,000
Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Assets held at fair value		2,621,000,000
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Fair value of financial liabilities	759,000,000	837,000,000
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member] | Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Assets held at fair value		2,575,000,000
Uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Gains losses recognized in respect of asset held	0
Uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods [member] | Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Assets held at fair value		14,000,000
Listed bonds and other long-term borrowings [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Fair value of financial liabilities	17,507,000,000	14,878,000,000
Carrying value of financial liabilities	16,212,000,000	13,491,000,000
Finance leases [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Fair value of financial liabilities	245,000,000	253,000,000
Carrying value of financial liabilities	£ 218,000,000	£ 223,000,000

Financial Instruments and Ris_4

Financial Instruments and Risk Management - Summary of Fair Value of Derivative Financial Assets and Liabilities Estimated Using Discounted Cash Flow Models, Market Rates and Foreign Exchange (Detail) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Total assets	£ 1,837	£ 4,137
Total liabilities	759	837
Fair value through other comprehensive income [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value	53
Fair value through profit and loss [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value	6	7
Derivative financial assets	257	261
Derivative financial liabilities	195	209
Designated in a hedge [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Derivative financial assets	1,521	1,248
Derivative financial liabilities	564	628
Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value		2,621
Uses quoted prices in active markets for identical assets or liabilities [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Total assets	44	39
Uses quoted prices in active markets for identical assets or liabilities [member] | Fair value through other comprehensive income [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value	38
Uses quoted prices in active markets for identical assets or liabilities [member] | Fair value through profit and loss [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value	6	7
Uses quoted prices in active markets for identical assets or liabilities [member] | Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value		32
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Total assets	1,778	4,084
Total liabilities	759	837
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member] | Fair value through profit and loss [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Derivative financial assets	257	261
Derivative financial liabilities	195	209
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member] | Designated in a hedge [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Derivative financial assets	1,521	1,248
Derivative financial liabilities	564	628
Uses inputs for the asset or liability other than quoted prices, that are observable either directly or indirectly [member] | Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value		2,575
Uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Total assets	15	14
Uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods [member] | Fair value through other comprehensive income [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value	£ 15
Uses inputs for the asset or liability that are not based on observable market data, such as internal models or other valuation methods [member] | Available for sale [member]
Disclosures of fair value hierarchy of financial assets and financial liabilities [line items]
Investment at fair value		£ 14

Financial commitments - Additio

Financial commitments - Additional Information (Detail) - GBP (£) £ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Financial Commitments [Abstract]
Capital commitments	£ 1,293	£ 993	£ 875
Programme rights commitments	£ 2,866	£ 2,823	£ 1,955

Post balance sheet events - Add

Post balance sheet events - Additional Information (Detail) £ in Millions	6 Months Ended
	Sep. 30, 2018GBP (£)	Sep. 30, 2017GBP (£)	Oct. 01, 2018Employees
Disclosure of non-adjusting events after reporting period [line items]
Revenue	£ 11,588	£ 11,786
Internal cost	9,896	10,332
Elimination of intersegment amounts [member]
Disclosure of non-adjusting events after reporting period [line items]
Revenue	(1,578)	(1,672)
Business and public sector segment [member] | Elimination of intersegment amounts [member]
Disclosure of non-adjusting events after reporting period [line items]
Revenue	10
Internal cost	10
Wholesale and ventures segment [member] | Elimination of intersegment amounts [member]
Disclosure of non-adjusting events after reporting period [line items]
Revenue	10
Internal cost	10
Openreach [member]
Disclosure of non-adjusting events after reporting period [line items]
Revenue	£ 2,472	£ 2,548
Number of employees transferred | Employees			31,000

Related party transactions - Ad

Related party transactions - Additional Information (Detail) - British Telecommunications PLC [member] - GBP (£) £ in Millions	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2002
Disclosure of transactions between related parties [line items]
Investment in the company			£ 18,500
Final dividend declared	£ 2,500	£ 0

Related party transactions - Ba

Related party transactions - Balances with Parent and Ultimate Parent Companies and Finance Income or Expense (Detail) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Apr. 01, 2018	Mar. 31, 2018
Disclosure of transactions between related parties [line items]
Non-current liabilities loans	£ 15,317		£ 13,038	£ 13,038	[1]
Current liabilities loans	4,290		£ 2,298	2,298	[1]
Finance income	147	£ 101
Finance (expense)	386	381
Ultimate Parent Company [member]
Disclosure of transactions between related parties [line items]
Non-current assets investments	3,024			2,983
Non-current liabilities loans	(1,061)			(1,044)
Trade and other receivables	16			15
Current asset investments	30			34
Current liabilities loans	(1,477)			(18)
Finance income	30	13
Finance (expense)	(22)	(9)
British Telecommunications PLC [member]
Disclosure of transactions between related parties [line items]
Non-current assets investments	10,486			10,318
Current asset investments	105			168
Trade and other payables	(73)			£ (50)
Finance income	£ 105	£ 84
[1]	Restatement to reflect the update to our retirement benefit obligation. See Note 2 to the condensed consolidated financial statements