Exhibit 5.1
                                                                   -----------

               SIDLEY AUSTIN (UK) LLP     BEIJING    GENEVA       SAN FRANCISCO
               WOOLGATE EXCHANGE          BRUSSELS   HONG KONG    SHANGHAI
SIDLEY AUSTIN  25 BASINGHALL STREET       CHICAGO    LONDON       SINGAPORE
- -------------  LONDON EC2V 5HA            DALLAS     LOS ANGELES  TOKYO
SIDLEY         DX NUMBER 580 LONDON CITY  FRANKFURT  NEW YORK     WASHINGTON, DC
               +44 (0) 20 7360 3600
               +44 (0) 20 7626 7937 FAX




Granite Master Issuer plc
Fifth Floor
100 Wood Street
London
EC2V 7EX



                                                                  May 23, 2007



Dear Sirs


Granite Master Issuer plc (No. 5250668) Series 2007-2 Notes
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1.    INTRODUCTION

We have acted as English legal advisers to Granite Master Issuer plc (the
"Company") in connection with the issuance of U.S.$1,060,000,000 Series 2007-2
Class 1A1 Notes due April 2032, (euro)325,000,000 Series 2007-2 Class 1A2
Notes due April 2032, (pound)150,000,000 Series 2007-2 Class 1A3 Notes due
April 2032, U.S.$1,025,000,000 Series 2007-2 Class 2A1 Notes due December
2054, CAN$500,000,000 Series 2007-2 Class 2A2 Notes due December 2054,
U.S.$1,100,000,000 Series 2007-2 Class 3A1 Notes due December 2054,
(euro)1,000,000,000 Series 2007-2 Class 3A2 Notes due December 2054,
$1,000,000,000 Series 2007-2 Class 4A1 Notes due December 2054,
(pound)650,000,000 Series 2007-2 Class 4A2 Notes due December 2054,
U.S.$66,500,000 Series 2007-2 Class 1B1 Notes due December 2054,
U.S.$53,500,000 Series 2007-2 Class 2B1 Notes due December 2054,
U.S.$35,000,000 Series 2007-2 Class 3B1 Notes due December 2054,
(euro)100,000,000 Series 2007-2 Class 3B2 Notes due December 2054,
(pound)53,000,000 Series 2007-2 Class 3B3 Notes due December 2054,
U.S.$64,000,000 Series 2007-2 Class 1M1 Notes due December 2054,
U.S.$52,000,000 Series 2007-2 Class 2M1 Notes due December 2054,
(euro)162,000,000 Series 2007-2 Class 3M2 Notes due December 2054,
(pound)20,000,000 Series 2007-2 Class 3M3 Notes due December 2054,
U.S.$50,000,000 Series 2007-2 Class 2C1 Notes due December 2054,
(euro)52,000,000 Series 2007-2 Class 2C2 Notes due December 2054,
(euro)84,500,000 Series 2007-2 Class 3C2 Notes due December 2054 and
(pound)60,000,000 Series 2007-2 Class 3C3 Notes due December 2054 (the "Series
2007-2 Notes") by the Company.

1.1   Unless otherwise defined, capitalised terms defined in the Issue
      Documents (as defined below) have the same meanings when used in this
      letter.

1.2   We have examined copies of the documents mentioned in the Schedule
      hereto and






    Sidley Austin (UK) LLP is a limited liability partnership formed and
                      registered under the laws of the
    State of Delaware. The offices listed above (other than London) are
             offices of associated Sidley Austin partnerships.

  A list of partners' names and their professional qualifications is open
                    for inspection at Woolgate Exchange
      25 Basinghall Street, London, EC2V 5HA. All partners are either
                 solicitors or registered foreign lawyers.

                         Regulated by the Law Society.




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      such other documents as we have considered necessary.

1.3   We have not made any investigation of, and do not express any opinion
      on, the law of any jurisdiction other than England and Wales.

1.4   The headings to paragraphs in this letter are for information purposes
      only and shall not otherwise form part of this letter.

2.    ASSUMPTIONS

2.1   In considering the documents referred to above and in rendering this
      opinion we have, without any further enquiry, assumed (save as expressly
      stated):

      (a)   the capacity, power and authority of each of the parties (other
            than the Company) to execute, deliver and perform the terms of the
            documents specified in Part I of Schedule (together, the "Issue
            Documents");

      (b)   the due execution and delivery of the Issue Documents;

      (c)   the conformity to original documents of any copy documents
            examined by us and that the copy of the Memorandum and Articles of
            Association of the Company examined by us is complete and up to
            date and would, if issued today, comply, as respects the Articles
            of Association, with Section 380 of the Companies Act 1985;

      (d)   that the Series 2007-2 Notes have been duly executed, issued and
            authenticated in accordance with the provisions of the Amended and
            Restated Issuer Trust Deed, the Issuer Paying Agent and Agent Bank
            Agreement and the Tenth Supplemental Trust Deed (each as defined
            in the Schedule);

      (e)   that no law of any jurisdiction outside England and Wales would
            render execution, delivery or issue illegal or ineffective and
            that, insofar as any obligation under any of the Issue Documents
            or the Series 2007-2 Notes is performed in, or is otherwise
            subject to, any jurisdiction other than England and Wales, its
            performance will not be illegal or ineffective by virtue of the
            law of that jurisdiction;

      (f)   that the information disclosed by our searches made today of the
            records at the office of the Registrar of Companies in London and
            at the Central Registry of Winding up petitions in relation to the
            Company was then complete, up to date and accurate and has not
            since then been materially altered or added to, and no notice of
            intention to appoint an administrator or an application for an

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            administration order in respect of the Company has been presented
            or filed in any court in England and Wales;

      (g)   that the Company is not, on the date hereof, unable to pay its
            debts within the meaning of section 123 of the Insolvency Act 1986
            (as amended) and will not become unable to do so in consequence of
            the transactions effected by the Issue Documents;

      (h)   that the Minutes referred to in Part II of the Schedule represent
            a true record of the proceedings described therein of duly
            convened, constituted and quorate meetings of the Boards of
            Directors of the Company acting in the interests and for a proper
            purpose of the Company and that the relevant meetings will be duly
            held and that the authorisations to be given thereat will not
            subsequently been revoked or amended;

      (i)   that any factual matters referred to in each Issue Document will
            be true and accurate (including, without limitation, the accuracy
            of the representations and warranties therein);

      (j)   that the relevant Issue Documents have, in all material respects
            relevant hereto, been executed and delivered substantially in the
            form of the relevant exhibit to the Registration Statement;

      (k)   that none of the parties to the Issue Documents has taken or will
            take any action in relation to the Series 2007-2 Notes (i) which
            would be a contravention of Section 19 of the Financial Services
            and Markets Act 2000 (the "FSMA") or (ii) in consequence of
            anything said or done by a person in the course of carrying on
            investment business (within the meaning of the FSMA) in
            contravention of that Section;

      (l)   that (i) none of the Issue Documents will be entered into and none
            of the Series 2007-2 Notes will be issued in consequence of a
            communication in relation to which there has been or will be a
            contravention of Section 21 of the FSMA and (ii) no person has
            communicated or will communicate any inducement or invitation to
            engage in investment activity (within the meaning of the FSMA) in
            connection with the Issue Documents or the issue of the Series
            2007-2 Notes in contravention of Section 21 of the FSMA; and

      (m)   that any party to any of the Issue Documents which is subject to
            the supervision of any regulatory authority in the United Kingdom
            has complied and will comply with the requirements of such
            regulatory authority in connection with the issue, offering or
            sale of the Series 2007-2 Notes.

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      We express no opinion as to matters of fact.

3.    OPINION

      Based on the foregoing and subject to such legal and other
      considerations and qualifications as are stated herein, we are of the
      opinion that the Series 2007-2 Notes will constitute valid and legally
      binding obligations of the Company. As a result, those obligations would
      be enforceable in proceedings before the English courts.

4.    QUALIFICATIONS

      The opinions given in paragraph 3 of this letter are subject to the
      following qualifications:

      (a)   We do not express any opinion on European Community law as it
            affects any jurisdiction other than England and Wales.

      (b)   Any enforcement of the obligations of the Company in proceedings
            before the English courts would be by way of grant of a remedy in
            the event of a breach of those obligations. The nature and
            availability of the remedies provided by the English courts would
            depend on the circumstances. These remedies, including an order by
            the court requiring the payment of damages or the payment of a sum
            due, would be available subject to the principles of law, equity
            and procedures of general application. Some remedies, including an
            order by the court requiring specific performance of an obligation
            or the issue of an injunction, would be entirely within the
            discretion of the court. The possibility of obtaining any remedy
            would be lost if proceedings were not to be commenced within
            certain time limits. The English courts have power to stay
            proceedings and may decline jurisdiction, notably if concurrent
            proceedings are brought elsewhere. Accordingly, enforcement of the
            obligations of the Company under the Series 2007-2 Notes would not
            be certain in every circumstance.

(c)         The obligations of the Company under the Series 2007-2 Notes will
            be subject to any law from time to time in force relating to
            liquidation or administration or any other law or legal procedure
            affecting generally the enforcement of creditors' rights.

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5.          GENERAL

      We hereby consent to the filing of this opinion as an exhibit to the
      Company's Report on Form 8-K dated the date hereof.


Yours faithfully,



/s/ Sidley Austin (UK) LLP

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                                   SCHEDULE

                                    PART I

1.    The issuer trust deed dated 19 January 2005 between the Company and The
      Bank of New York, exhibited as Exhibit 4.6.1 to the Registration
      Statement (the "Issuer Trust Deed").

2.    The tenth supplemental issuer trust deed between the Company and The
      Bank of New York dated 23 May 2007 relating to the issue of the Series
      2007-2 Notes (the "Supplemental Issuer Trust Deed").

3.    The issuer paying agent and agent bank agreement amended and restated on
      25 January 2005 between, inter alios, the Company and Citibank, N.A.,
      exhibited as Exhibit 4.7 to the Registration Statement (the "Amended and
      Restated Issuer Paying Agent and Agent Bank Agreement").

4.    The Form of Global Note Certificate for each Class of Series 2007-2
      Notes.



                                    PART II

The Minutes of a Meeting of the Board of Directors of the Company held on 17
May 2007.


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