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                                                                     EXHIBIT 4.4

                                AMENDMENT TO THE

             GELSENBERG PARTICIPATION AGREEMENT DATED JULY 15, 2001



                                 by and between

                                     BP plc;

                       Britannic House, 1 Finsbury Circus,
                                 London EC2M 7BA



                                       and



                                 Deutsche BP AG,

                         Max-Born-Str. 2, 22761 Hamburg



                                       and



                                    E.ON AG,

                         E.ON-Platz 1, 40479 Dusseldorf



                                       and

                    E.ON Zehnte Verwaltungsgesellschaft mbH,

                         E.ON-Platz 1, 40479 Dusseldorf



WHEREAS in the Gelsenberg Partcipation Agreement dated July 15, 2001 (the "PA")
the parties agreed to establish a joint venture in Gelsenberg Aktiengesellschaft
("Gelsenberg") with E.ON AG ("E.ON") as a 51% shareholder and BP p.l.c. ("BP")
as a 49% shareholder by way of a capital increase with effect as of the
Effective Date, i.e. the first day of the calendar month following obtainment of
all Required Approvals.

WHEREAS in the PA a Put Option is granted to the joint venture partner BP for
their minority stake in Gelsenberg exercisable from 1 January 2002.

WHEREAS the Required Approvals (in the given situation, the approval by the
Bundesminister fur Wirtschaft und Technologie pursuant to Section 42 GWB), have
not yet been received.

WHEREAS RAG Aktiengesellschaft (formerly Ruhrkohle Aktiengesellschaft) has
waived all pre-emption rights pursuant to the two agreements between Deutsche BP
and Ruhrkohle Aktiengesellschaft dated 27 April 1979.

WHEREAS BP has come to the conclusion that it intends to exit the joint venture
immediately upon its establishment.
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WHEREAS the parties agree that instead of establishing a joint venture with BP
immediately exercising its put option in accordance with the provisions of the
PA, BP shall directly sell and transfer its existing shares in Gelsenberg to
E.ON under economic terms equivalent to those which would apply pursuant to the
PA.

WHEREAS the parties agree that E.ON may nominate E.ON Zehnte
Verwaltungsgesellschaft mbH as the acquirer of BP's one million bearer shares in
Gelsenberg in its stead, notwithstanding E.ON remaining jointly and severally
liable.

WHEREAS the parties agree that Deutsche BP AG ("DBP") may be nominated by BP as
the seller of the one million bearer shares in Gelsenberg, notwithstanding BP
remaining jointly and severally liable:

NOW, THEREFORE, the parties agree as follows (all defined terms, unless
otherwise mentioned, having the meaning as defined in the PA):

1        Clause 4.1 of the PA shall be amended as follows:

         "Each of E.ON and BP agrees that E.ON shall purchase, and BP shall
         sell, BP's 1 million bearer shares in Gelsenberg with economic effect
         as of the Effective Date subject to the conditions of Clause 2.1 and
         pursuant to the terms of this Agreement."

2        The introduction to Clause 4.2 of the PA shall be amended as follows:

         "Both, E.ON and BP, agree that they shall or shall procure that a
         member of the E.ON Group or BP Group, respectively, carries out the
         following:"

3        Clauses 4.2.1 - 4.2.6 of the PA shall be deleted.

4        Clause 4.2.8 of the PA shall be amended as follows:

         "Deutsche BP shall, to the extent legally permissible, procure that

         (i)      all of the members of the supervisory board of Gelsenberg
                  shall resign with effect from the Effective Date, and

         (ii)     the Gelsenberg representative on the supervisory board of
                  Ruhrgas shall resign and be replaced by an E.ON nominee with
                  effect from the Effective Date."

5        Clauses 4.2.9 - 4.2.11 of the PA shall be deleted.

6        Clause 8 of the PA shall be replaced by the following new Clause:

         "8.      PURCHASE PRICE, TRANSFER AND ASSIGNMENT OF THE SHARES

         8.1      The preliminary purchase price for the shares, which shall be
                  subject to adjustment pursuant to Clause 9, shall amount to
                  Euro 400,000,000 (Euro two billion and four hundred million;
                  the "Preliminary Purchase Price") and shall be due and payable
                  in accordance with Clause 8.3.

         8.2      The one million bearer shares held by Gelsenberg are
                  documented in one share certificate (Globalaktie Nr. 5),
                  issued November 10, 1992 with the share numbers 5.759.971 to
                  No. 6.209.860 and 6.209.891 to. 6.760.000. DBP hereby
                  transfers and assigns to E.ON which hereby accepts such
                  transfer and assignment, its 1 million bearer shares in
                  Gelsenberg with a nominal value of DM 100 each subject to and
                  legally effective immediately upon fulfillment of the
                  following conditions precedent and hereby irrevocably
                  instructs Deutsche Bank as the Escrow Agent,

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                  which at the signing hereof receives in escrow the aforesaid
                  share certificate to hold it for and hand it out to E.ON as
                  soon as the following conditions precedent have been
                  fulfilled:

                  8.2.1   receipt by E.ON of an unconditional (ohne Bedingungen
                          im Rechtssinne) approval of the Bundesminister fur
                          Wirtschaft und Technologie for the acquisition as
                          filed with the German cartel authorities on 15 August
                          2001, or

                  8.2.2   if an approval of the Bundesminister fur Wirtschaft
                          und Technologie for the acquisition as filed with the
                          German cartel authorities on 15 August 2001 is subject
                          to conditions (Bedingungen im Rechtssinne),
                          satisfaction of these conditions by E.ON, and

                  8.2.3   payment by E.ON of the full amount of the Preliminary
                          Purchase Price to an escrow account pursuant to Clause
                          8.3 and the remaining in such account of the full
                          amount until the conditions in Clauses 8.2.1 or 8.2.2
                          have been satisfied.

                  E.ON shall use all reasonable endeavours to procure
                  satisfaction of all conditions to an approval of the
                  Bundesminister fur Wirtschaft und Technologie, if any.

         8.3      Payment of the Preliminary Purchase Price shall be effected by
                  way of including Deutsche Bank AG as an escrow agent in
                  accordance with the Escrow Agreement attached hereto in draft
                  form as Exhibit A not later than on 27 June 2002, and, in
                  accordance therewith, by payment of the Preliminary Purchase
                  Price to an escrow account which the parties shall establish
                  immediately following the signing of this Amendment with the
                  escrow agent.

                 8.3.1    E.ON shall pay the full amount of the Preliminary
                          Purchase Price into the escrow account at the latest
                          on July 1 2002; earlier payments shall be permissible
                          at any given time. If the aforesaid approval has not
                          been granted by 15 August 2002, E.ON following a 3
                          Business Days advance written notification addressed
                          to the escrow agent with a copy to BP shall be
                          entitled to request repayment of any amounts paid by
                          E.ON into the escrow account and interest accrued.

                 8.3.2    The full credit balance (other than interest) on the
                          escrow account shall solely be attributable to BP from
                          and including the day, the condition precedent
                          pursuant to Clauses 8.2.1 and 8.2.2 are fulfilled. As
                          of this moment, BP shall be the sole beneficiary of
                          the escrow account.

                 8.3.3    E.ON shall immediately inform BP and the escrow agent
                          in writing by telefax notice of the receipt of the
                          approval by the Bundesminister fur Wirtschaft und
                          Technologie, conditions to it, if any, and the
                          satisfaction of such conditions, if any.

                 8.3.4    Interest accrued on the escrow account until (but
                          excluding the day of) receipt of an unconditional
                          approval of the Bundesminister fur Wirtschaft und
                          Technologie pursuant to Section 42 GWB or until the
                          satisfaction of the conditions thereto, if any, shall
                          be attributable to E.ON and paid out to E.ON by the
                          escrow agent following the information to be rendered
                          by E.ON pursuant to Clause 8.3.3, interest accrued
                          thereafter shall be attributable and be paid out to
                          BP.
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                 8.3.5    BP shall at the latest on the Effective Date pay to
                          E.ON interest at LIBOR (as defined in the PA) on the
                          Preliminary Purchase Price for the period from and
                          including the date of payment of the Preliminary
                          Purchase Price into the escrow account or receipt or
                          unconditionality of the approval by the Bundesminister
                          fur Wirtschaft und Technologie, whatever is the later,
                          until and excluding the Effective Date."

7        Clause 9 of the PA shall be amended as follows:

         "9.      ADJUSTMENT OF THE PRELIMINARY PURCHASE PRICE

         Each of E.ON and BP agrees that the Preliminary Purchase Price shall be
         adjusted to reflect the following:

         9.1      a deduction of any amount validly claimed by E.ON and agreed
                  by BP in respect of a breach of warranty by BP pursuant to
                  clause 5.1 above in the period between signing this PA and the
                  Gelsenberg Economic Transfer Date. If no agreement is reached,
                  E.ON may still claim such amount as a breach of warranty
                  pursuant to this Agreement;

         9.2      an adjustment in respect of the amount which E.ON and BP shall
                  agree represents:

                 9.2.1    Retained Earnings of the Gelsenberg Group on a
                          consolidated basis for the period from 1 January 2001
                          to the Effective Date. Retained Earnings means the
                          earnings of the Gelsenberg Group generated by its
                          operations after deduction of net interest,
                          depreciation, amortisation, taxation, minority
                          interests and distributions.

                 (i)      Retained Earnings shall be calculated in accordance
                          with German GAAP and following Gelsenberg's existing
                          accounting policies, procedures and practices
                          consistently applied in drawing up the Gelsenberg
                          Group for the financial years ending on 31 December
                          2000, provided, however, that the actual dividend paid
                          by Ruhrgas to Gelsenberg in 2002 shall be allocated
                          pro rata temporis to each month of the calendar year
                          2002 irrespective of whether such dividend is paid
                          before or after the Effective Date.

                 (ii)     Each of E.ON and BP agrees that if the Ruhrgas
                          dividend payable to Gelsenberg for 2002 has not been
                          paid at the Effective Date, then the parties shall
                          agree an estimated dividend based on the dividend paid
                          by Ruhrgas to Gelsenberg for the year ending 2001
                          which amount shall be subsequently adjusted once the
                          actual Ruhrgas dividend for 2002 is paid.

                 9.2.2    an agreed proportion of the revenue expenditure
                          incurred by the Gelsenberg Group in excess of the
                          amount set out in the Reserved Matters in respect of
                          such revenue expenditure otherwise than in the
                          ordinary course of business.

         9.3      To the extent possible, any payment required by this Clause 9
                  shall be paid within 5 Business Days of the agreement or
                  determination of such adjustments. Such payments shall bear
                  interest at LIBOR from (and including) the Effective Date
                  until (but excluding) the date of payment.

         9.4      The relevant amounts as of the Effective Date for calculation
                  of the adjustments pursuant to Clause 9.2.1 shall be
                  calculated on the basis of audited interim financial
                  statements of the Gelsenberg Group. E.ON and BP shall procure
                  on a basis

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                  and timetable to be agreed that Gelsenberg's auditors
                  appointed to audit the Gelsenberg financial statements of 2001
                  draw up an audited interim financial statement of the
                  consolidated Gelsenberg Group (based on German GAAP and
                  consistent with the accounting policies for the Accounts for
                  the year ended 31 December 2000) as of the Effective Date.

         9.5      BP agrees to indemnify and hold E.ON harmless against any
                  liability, loss or cost suffered by Gelsenberg as a result of
                  AGIP failing to comply with its existing contractual
                  obligations to make payments to Gelsenberg in respect of
                  pensions and related costs of former employees of RVI."

         The repetition of the wording of Clause 9.2 of the PA in this Amendment
         shall not prejudice different opinions E.ON and BP are having with
         respect to the proper interpretation of this Clause 9.2 and the
         calculation of Retained Earnings.

8        Clause 10 of the PA shall be deleted.

9        Clause 11.1 of the PA shall remain in full force. The words
         "Subscription Date" shall be replaced by "Effective Date". Clause 11.2
         of the PA shall be replaced by the following new Clause:

         "BP shall be entitled to rescind the PA if E.ON, notwithstanding a
         written notice from BP after payment has been falling due, has not paid
         the Preliminary Purchase Price into the escrow account pursuant to
         Clause 8.3 of the PA (as amended) within a grace period of 3 Business
         Days."

         The following new Clause 11.3 shall be added to the PA:

         "In case of a rescission, the escrow agent shall repay to E.ON any
         amounts paid into the escrow account plus interest accrued. Should the
         receiver of a notice of rescission contest the validity of the
         rescission, the escrow agent shall be entitled to withhold repayment of
         the funds in escrow until the parties have reached an agreement or a
         final and binding decision (including a decision by the arbitral
         tribunal pursuant to Clause 13.9.2 of the PA) has been issued.
         Contractual or statutory claims and rights of the parties against each
         other, irrespective of their legal ground, shall not be affected by a
         rescission."

10       Clause 12 of the PA shall be deleted.

11       All provisions of the PA not deleted or amended by this Amendment
         Agreement shall remain unchanged and in full force and effect.

12       E.ON hereby nominates E.ON Zehnte Verwaltungsgesellschaft mbH as the
         acquirer of BP's 1 million bearer shares in its stead and E.ON Zehnte
         Verwaltungsgesellschaft mbH hereby joins as additional party and
         accepts all terms and conditions of the PA as amended hereby such that
         upon fulfilment of the conditions E.ON Zehnte Verwaltungsgesellschaft
         mbH shall directly acquire title to BP's one million bearer shares in
         Gelsenberg. E.ON expressly confirms that it remains a party to the PA
         and is jointly and severally liable with E.ON Zehnte
         Verwaltungsgesellschaft mbH for all obligations and liabilities arising
         thereunder. BP hereby agrees to the aforesaid nomination of E.ON Zehnte
         Verwaltungsgesellschaft mbH as acquirer and additional party to the PA.

13       BP hereby nominates DBP as the seller and transferor of the 1 million
         bearer shares of Gelsenberg and DBP hereby joins as an additional party
         and accepts all terms and conditions of the PA as amended hereby such
         that upon fulfilment of the conditions DBP shall directly sell and
         transfer title to the shares and receive the consideration. BP
         expressly confirms

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         that it remains a party to the PA and is jointly and severally liable
         with DPB. E.ON AG and E.ON Zehnte Verwaltungsgesellschaft mbH agree to
         the accession of DBP as seller and additional party to the PA.


                        , this     June 2002
------------------------       ---


BP p.l.c.:                         Deutsche BP AG:



E.ON AG:                           E.ON Zehnte Verwaltungsgesellschaft mbH: