Exhibit 5.1




BP p.l.c.
Britannic House
1 Finsbury Circus
London EC2M 7BA

BP Capital Markets p.l.c.
Breakspear Park
Breakspear Way
Hemel Hempstead

Herts  HP2 4UL

                     21 February 2002


Dear Sirs,

In connection with the registration under the Securities Act of 1933, as amended
(the "Act"), of US$6,000,000,000 aggregate amount of guaranteed debt securities
(the "Securities") of BP Capital Markets America Inc., a Delaware corporation BP
Capital Markets p.l.c., an English company ("BP Capital"), BP Canada Finance
Company, a Canadian company and BP Australian Capital Markets Limited, an
Australian company (each an "Issuer" and collectively, the "Issuers"), and the
related guarantees (the "Guarantees") of the Securities by BP p.l.c., an English
company ("BP"), as Group General Counsel of BP, I have examined such corporate
records, certificates and other documents and such questions of law as I have
considered necessary or appropriate for the purposes of this opinion.

Upon the basis of such examination, I advise you that, in my opinion:

1.   each of BP and BP Capital is a public limited company duly incorporated in
     England and Wales under the Companies Act 1985;

2.   when the Registration Statement has become effective under the Act, the
     respective Indentures relating to the Securities to be issued by each
     Issuer have been duly authorized, executed and delivered, the terms of the
     Securities and the Guarantees and of the issuance and sale of the
     Securities and the Guarantees have been duly established in conformity with
     the Indenture relating to such Securities so as not to violate any
     applicable law or result in a default under or breach of an agreement or
     instrument then binding upon the Issuers or BP, the Securities to be issued
     have been duly executed and authenticated in accordance with the Indenture
     relating to such Securities, and the Securities and the Guarantees have
     been issued and sold as contemplated in the Registration Statement, the
     Guarantees will constitute valid and legally binding obligations of BP;

3.   when the Registration Statement has become effective under the Act, the
     Indenture relating to the Securities to be issued by BP Capital has been
     duly authorized, executed and delivered, the terms of the Securities of BP
     Capital and the Guarantees and of the issuance and sale of the Securities
     of BP Capital and the Guarantees have been duly established in conformity
     with the Indenture relating to such Securities so as not to violate any
     applicable law or result in a default under or breach of an agreement or
     instrument then binding on BP Capital or BP, the Securities of BP Capital
     have been duly executed and authenticated and the Guarantees have been duly
     executed in each case in accordance with the Indenture relating thereto,
     and the Securities of BP Capital and the Guarantees have been issued and
     sold as contemplated in the Registration Statement, the



     Securities of BP Capital will constitute valid and legally binding
     obligations of BP Capital; and

4.   I confirm to you that my opinion is as set forth under the caption "Tax
     Considerations - United Kingdom Taxation" in the Prospectus included in the
     Registration Statement.

The foregoing opinion is limited to the laws of England in force on this date
and I am expressing no opinion as to the effect of the laws of any other
jurisdiction. I understand you are relying as to all matters governed by the
laws of the state of New York upon the opinion dated February 21, 2002 of Daniel
B. Pinkert, special United States counsel to BP, which opinion is being
delivered to you by such counsel.

I consent to the filing of this opinion as an exhibit to the Registration
Statement relating to the Securities and the Guarantees and to the references to
me under the captions "Tax Considerations - United Kingdom Taxation" and
"Validity of Securities" in the Prospectus included therein. In giving such
consent I do not thereby admit that I am within the category of persons whose
consent is required under Section 7 of the Act.

Yours faithfully,

/s/ P.B.P. Bevan