Document:

<PAGE>

                                                                  EXHIBIT 10.18

                                                                 EXECUTION COPY

                             LETTER AMENDMENT NO. 2

                                        Dated as of October 25, 2002

To the banks, financial institutions
   and other institutional lenders
   (collectively, the "Lenders") parties
   to the Credit Agreement referred to
   below and to Citibank, N.A., as agent
   (the "Agent") for the Lenders

Ladies and Gentlemen:

                  We refer to the Credit Agreement dated as of June 21, 2002, as
amended by the Letter Amendment dated as of October 4, 2002 (the "Credit
Agreement") among the undersigned and you. Capitalized terms not otherwise
defined in this Letter Amendment have the same meanings as specified in the
Credit Agreement.

                  It is hereby agreed by you and us that Section 5.02(f) of the
Credit Agreement is, effective as of the date of this Letter Amendment, hereby
amended as follows:

                  (a)      Clauses (iv) and (v) are relettered as clauses (v)
and (vi), respectively, and

                  (b)      A new clause (iv) is added immediately after clause
(iii) to read as follows:

                  "(iv)    Debt consisting of Guaranteed Senior Notes due 2007
         of Platinum Underwriters Finance, Inc. included in the Borrower's
         equity security units in an aggregate amount outstanding not to exceed
         $172,500,000,"

                  This Letter Amendment shall become effective as of the date
first above written when, and only when, on or before October 28, 2002, the
Agent shall have received counterparts of this Letter Amendment executed by the
undersigned and the Required Lenders or, as to any of the Lenders, advice
satisfactory to the Agent that such Lender has executed this Letter Amendment.
This Letter Amendment is subject to the provisions of Section 8.01 of the Credit
Agreement.

                  On and after the effectiveness of this Letter Amendment, each
reference in the Credit Agreement to "this Agreement", "hereunder", "hereof" or
words of like import referring to the Credit Agreement, and each reference in
the Notes to "the Credit Agreement", "thereunder", "thereof" or words of like
import referring to the Credit Agreement, shall mean and be a reference to the
Credit Agreement, as amended by this Letter Amendment.

<PAGE>

                  The Credit Agreement and the Notes, as specifically amended by
this Letter Amendment, are and shall continue to be in full force and effect and
are hereby in all respects ratified and confirmed. The execution, delivery and
effectiveness of this Letter Amendment shall not, except as expressly provided
herein, operate as a waiver of any right, power or remedy of any Lender or the
Agent under the Credit Agreement, nor constitute a waiver of any provision of
the Credit Agreement.

                  If you agree to the terms and provisions hereof, please
evidence such agreement by executing and returning at least two counterparts of
this Letter Amendment to Susan L. Hobart, Shearman & Sterling, 599 Lexington
Avenue, New York, New York 10022.

                  This Letter Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Letter Amendment by telecopier shall be
effective as delivery of a manually executed counterpart of this Letter
Amendment.

                  This Letter Amendment shall be governed by, and construed in
accordance with, the laws of the State of New York.

                                   Very truly yours,

                                   PLATINUM UNDERWRITERS HOLDINGS,
                                   LTD.

                                   By  /s/ Jerome T. Fadden
                                       -----------------------------------------
                                       Title: President and Chief Executive
                                              Officer

Agreed as of the date first above written:

CITIBANK, N.A.,
      as Agent and as Lender

By _______________________________________
   Title:

JPMORGAN CHASE BANK

By _______________________________________
   Title:

<PAGE>

                  The Credit Agreement and the Notes, as specifically amended by
this Letter Amendment, are and shall continue to be in full force and effect and
are hereby in all respects ratified and confirmed. The execution, delivery and
effectiveness of this Letter Amendment shall not, except as expressly provided
herein, operate as a waiver of any right, power or remedy of any Lender or the
Agent under the Credit Agreement, nor constitute a waiver of any provision of
the Credit Agreement.

                  If you agree to the terms and provisions hereof, please
evidence such agreement by executing and returning at least two counterparts of
this Letter Amendment to Susan L. Hobait Shearman & Sterling, 599 Lexington
Avenue, New York, New York 10022.

                  This Letter Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Letter Amendment by telecopier shall be
effective as delivery of a manually executed counterpart of this Letter
Amendment.

                  This Letter Amendment shall be governed by, and construed in
accordance with, the laws of the State of New York.

                                             Very truly yours,

                                            PLATINUM UNDERWRITERS HOLDINGS, LTD.

                                            By _________________________________
                                               Title:

Agreed as of the date first above written:

CITIBANK, N.A.,
         as Agent and as Lender

By /s/ MICHAEL TAYLOR
   ----------------------------------
   Title: Vice President

JPMORGAN CHASE BANK

By /s/ Helen L. Newcomb
   __________________________________
   Title:

<PAGE>

BANK OF AMERICA, N.A.

By /s/ Leslie Reed
   ----------------------------------
   Title: Vice President

FLEET NATIONAL BANK

By __________________________________
   Title:

STATE STREET BANK AND TRUST COMPANY

By __________________________________
   Title:

<PAGE>

BANK OF AMERICA, N.A.

By __________________________________
   Title:

FLEET NATIONAL BANK

By /s/ [ILLEGIBLE]
   ----------------------------------
   Title: Portfolio Manager

STATE STREET BANK AND TRUST COMPANY

By /s/ Edward M. Anderson
   __________________________________
   Title:<PAGE>

                                                                  EXHIBIT 10.19

                                                                  EXECUTION COPY

                            DATED 1ST NOVEMBER, 2002

                      PLATINUM UNDERWRITERS HOLDINGS, LTD.

                                     - AND -

                            PLATINUM RE (UK) LIMITED

                            CAPITAL SUPPORT AGREEMENT

                                SLAUGHTER AND MAY
                                 ONE BUNHILL ROW
                                 LONDON EC1Y 8YY

                                  REF: GWJ/JCD

                                   CA023100048

<PAGE>

                                    CONTENTS

<TABLE>
<CAPTION>
CLAUSE                                                                             PAGE
<S>                                                                                <C>
1.    INTERPRETATION...........................................................      1

2.    OBLIGATION TO PROVIDE CAPITAL; CAPITAL REPAYMENT.........................      2

3.    TERM AND TERMINATION.....................................................      4

4.    CONTRACTS (RIGHTS OF THIRD PARTIES) ACT 1999.............................      5

5.    REMEDIES AND WAIVERS.....................................................      5

6.    AMENDMENTS...............................................................      5

7.    SPECIFIC PERFORMANCE.....................................................      5

8.    SUBROGATION..............................................................      6

9.    ASSIGNMENT...............................................................      6

10.   SEVERABILITY.............................................................      6

11.   ENTIRE AGREEMENT.........................................................      6

12.   NO PARTNERSHIP...........................................................      6

13.   NOTICES..................................................................      6

14.   GOVERNING LAW AND JURISDICTION...........................................      7

15.   COUNTERPARTS.............................................................      8
</TABLE>

<PAGE>

THIS AGREEMENT is made the 1st day of November, 2002

BETWEEN

1.    PLATINUM UNDERWRITERS HOLDINGS, LTD., a holding company organised under
      the laws of Bermuda ("PLATINUM HOLDINGS")

AND

2.    PLATINUM RE (UK) LIMITED, a company incorporated in England (registered
      number 4413755) whose registered office is at The St. Paul House, 27
      Camperdown Street, London, E1 8DS ("PLATINUM RE UK")

WHEREAS:

(A)   Platinum Re UK is a wholly-owned subsidiary of Platinum Regency Holdings
      ("Regency"), an Irish unlimited company, which is in turn a wholly-owned
      subsidiary of Platinum Holdings.

(B)   Platinum Re UK has applied to the Financial Services Authority for
      authorisation to carry on reinsurance business in the United Kingdom under
      Part IV of the Financial Services and Markets Act 2000 ("Authorisation").

(C)   Platinum Holdings is prepared to provide capital support to Platinum Re UK
      on the terms and subject to the conditions set out in this Agreement.

NOW IT IS HEREBY AGREED as follows:

1.    INTERPRETATION

1.1   In this Agreement, references to "SOURCEBOOK" are to the Interim
      Prudential sourcebook: Insurers published by the Financial Services
      Authority and as amended from time to time.

1.2   In construing this Agreement, unless otherwise specified:

      (A)   references to clauses are to clauses of this Agreement;

      (B)   headings to clauses are for convenience only and do not affect the
            interpretation of this Agreement;

      (C)   use of any gender includes the other gender;

      (D)   references to a "PERSON" shall be construed so as to include any
            individual, firm, company or other body corporate, government, state
            or agency of a state, local or municipal authority or government
            body or any joint venture, association or partnership (whether or
            not having separate legal personality);

<PAGE>
                                        2

      (E)   any reference to a "DAY" shall mean a period of 24 hours running
            from midnight to midnight;

      (F)   the expressions "HOLDING COMPANY", "SUBSIDIARY" and "SUBSIDIARY
            UNDERTAKING" shall have the meaning given in the Companies Act 1985;

      (G)   the expressions "MARGIN OF SOLVENCY" and "REQUIRED MINIMUM MARGIN"
            shall have the meanings given in the Sourcebook;

      (H)   references to writing shall include any modes of reproducing words
            in a legible and non-transitory form;

      (I)   a reference to any statute or statutory provision or provision of
            the Sourcebook shall be construed as a reference to the same as it
            may have been, or may from time to time be, consolidated, amended,
            modified or re-enacted;

      (J)   references to any English legal term for any action, remedy, method
            of judicial proceeding, legal document, legal status, court,
            official or any legal concept or thing shall in respect of any
            jurisdiction other than England be treated as including what most
            nearly approximates in that jurisdiction to the English legal term;
            and

2.    OBLIGATION TO PROVIDE CAPITAL; CAPITAL REPAYMENT

2.1   In the event that the accounts and statements of Platinum Re UK for any
      financial year of Platinum Re UK (the "annual financial statements")
      deposited by Platinum Re UK with the Financial Services Authority pursuant
      to Part I of Chapter 9 of the Sourcebook show that the margin of solvency
      of Platinum Re UK, determined in accordance with the rules set out in the
      Sourcebook and as shown by the Form 9 filed by Platinum Re UK as part of
      such annual financial statements, is less than 200% of the required
      minimum margin of Platinum Re UK calculated in accordance with Chapter 2
      of the Sourcebook, Platinum Holdings shall within 7 days of the date of
      the deposit of such annual financial statements make a loan to Platinum Re
      UK in such amount as is necessary to restore the margin of solvency of
      Platinum Re UK to a level equal to 200% of such required minimum margin of
      Platinum Re UK. For this purpose:

      (A)   such loan shall be subordinated in accordance with the provisions
            set out below; and

      (B)   in determining the amount to be so advanced by way of subordinated
            loan:

            (i)   regard shall be had only to the gross proceeds of such loan as
                  an asset;

            (ii)  in particular, but without limitation, no account shall be
                  taken in the calculation of the amount required to be advanced
                  hereunder by way of subordinated loan of the liability to
                  repay such subordinated loan; and

<PAGE>
                                       3

            (iii) in particular, but without limitation, no account shall be
                  taken in such calculation of paragraph 25 of Guidance Note 2.1
                  in volume 3 of the Sourcebook or any other rule or regulation
                  from time to time in force with regard to the treatment of
                  subordinated loans for the purposes of the maintenance of a
                  minimum margin of solvency.

2.2   Once Platinum Holdings shall have made any loan or loans to Platinum Re UK
      pursuant to clause 2.1, in determining whether Platinum Holdings is
      obliged to make any further advance to Platinum Re UK pursuant to clause
      2.1 in respect of any subsequent financial year of Platinum Re UK, the
      provisions of clause 2.1(B) shall apply, mutatis mutandis, in relation to
      such loan or loans in determining whether, and if so the extent to which,
      any such advance is required to be made.

2.3   Once Platinum Holdings shall have made any loan to Platinum Re UK pursuant
      to clause 2.1, where at the end of any subsequent financial year of
      Platinum Re UK the annual financial statements of Platinum Re UK for such
      financial year show that the margin of solvency of Platinum Re UK,
      determined in accordance with Chapter 2 of the Sourcebook (as modified by
      the provisions of clause 2.2 above), exceeds 200% of the required minimum
      margin of Platinum Re UK as shown by the Form 12 filed by Platinum Re UK
      as part of such annual financial statements, Platinum Re UK shall within 7
      days of the date of deposit of such annual financial statements repay to
      Platinum Holdings (save to the extent prohibited by law from time to time)
      such amount as is equal to the lesser of:

      (A)   the amount by which the margin of solvency of Platinum Re UK,
            determined as aforesaid, exceeds 200% of such required minimum
            margin of Platinum Re UK; and

      (B)   the principal amount then outstanding in respect of the loan made by
            Platinum Holdings to Platinum Re UK pursuant to clause 2.1.

2.4   (A)   Any loan made by Platinum Holdings to Platinum Re UK pursuant to
            clause 2.1 shall be interest-free.

      (B)   Platinum Holdings acknowledges and agrees that (save as set out in
            clause 2.3 or as otherwise provided in this Agreement) its rights to
            repayment of any amounts advanced by it to Platinum Re UK from time
            to time shall only arise and shall in all respects be subject to and
            conditional on the prior satisfaction in full of all other
            liabilities of Platinum Re UK save for sums due to any members of
            Platinum Re UK (in their capacity as such) on a winding-up of
            Platinum Re UK.

2.5   (A)   The obligations of Platinum Holdings to make advances as provided in
            this Agreement shall be absolute and unconditional under any and all
            circumstances and shall be continuing obligations and shall not be
            satisfied, discharged, impaired or otherwise affected except by
            performance thereof in full in accordance with the terms of this
            Agreement.

<PAGE>
                                       4

      (B)   Without prejudice to the generality of sub-clause 2.5(A) above,
            Platinum Holdings shall not be released or discharged from any of
            its obligations under this Agreement, nor shall any of such
            obligations be in any way prejudiced or affected by:

            (i)   the existence of any claim, set-off or other rights which
                  Platinum Holdings may have at any time against Platinum Re UK
                  or any other person;

            (ii)  any amendment of, or addition or supplement to, the terms of
                  any reinsurance contract to which Platinum Re UK is a party;

            (iii) any bankruptcy, insolvency, liquidation, amalgamation,
                  reconstruction, reorganisation, administration, administrative
                  or other receivership, or dissolution of Platinum Re UK or
                  Platinum Holdings; or

            (iv)  any other thing done or omitted or neglected to be done by any
                  person or any other dealing, fact, matter or thing which, but
                  for this provision, might operate to exonerate or discharge
                  Platinum Holdings from, or otherwise prejudice or affect, any
                  of Platinum Holdings' obligations under this Agreement.

2.6   Platinum Holdings shall be entitled at its election to discharge its
      obligations under this Clause 2 by advancing the relevant amount to
      Regency and procuring Regency to advance the same amount to Platinum Re UK
      on the same terms, mutatis mutandis, as the terms set out in this
      Agreement. In such event, the advance of any amount by Platinum Holdings
      to Regency shall be made on the basis that the obligation of Regency to
      repay any amount to Platinum Holdings which shall have been advanced to it
      hereunder shall be subject to Regency having been repaid such amount by
      Platinum Re UK in accordance with Clause 2.3.

3.    TERM AND TERMINATION

3.1   This Agreement shall take effect upon receipt by Platinum Re UK of
      Authorisation and shall continue in full force and effect until the third
      anniversary thereof unless terminated earlier in accordance with the
      provisions of sub-clause 3.2 below.

3.2   Platinum Holdings may terminate this Agreement by written notice to
      Platinum Re UK with immediate effect in the event that:

      (A)   Platinum Re UK ceases to write reinsurance business in the United
            Kingdom; or

      (B)   Platinum Holdings or one of its subsidiary companies ceases to own
            (directly or indirectly) a majority of the ordinary share capital of
            Platinum Re UK.

3.3   On termination of this Agreement whether pursuant to Clause 3.1 or Clause
      3.2, Platinum Holdings shall cease to have any further obligations under
      clauses 2.1 and 2.2

<PAGE>
                                       5

      but any such termination shall be without prejudice to Platinum Holdings'
      rights under clause 2.3.

4.    CONTRACTS (RIGHTS OF THIRD PARTIES) ACT 1999

      The Parties to this Agreement do not intend that any term of this
      Agreement shall be enforceable, by virtue of the Contracts (Rights of
      Third Parties) Act 1999, by any person who is not a party to this
      Agreement.

5.    REMEDIES AND WAIVERS

5.1   No failure or delay on the part of either party in exercising a right,
      power or remedy provided by this Agreement or by law shall operate as a
      waiver of that right, power or remedy or a waiver of any other rights,
      powers or remedies.

5.2   No single or partial exercise of a right, power or remedy provided by this
      Agreement or by law shall prevent further exercise of that right, power or
      remedy or the exercise of another right, power or remedy.

5.3   Except as otherwise provided herein, the rights, powers and remedies
      provided in this Agreement shall be cumulative and not exclusive of any
      rights, powers or remedies provided by law.

6.    AMENDMENTS

      This Agreement may only be amended or varied in writing signed by each of
      the parties hereto.

7.    SPECIFIC PERFORMANCE

      The parties hereto acknowledge that if any of the provisions of this
      Agreement were not to be performed in accordance with their specific terms
      or were otherwise to be breached, irreparable damage would occur and
      damages would not be an adequate remedy. In the event of any such breach,
      the aggrieved party shall be entitled, in addition to any other remedy at
      law or in equity, to specific performance of the terms hereof and
      immediate injunctive or other equitable relief, without the necessity of
      proving the inadequacy of money damages as a remedy or of posting any bond
      or other security.

8.    SUBROGATION

      Platinum Holdings shall have no rights (direct or indirect) of
      subrogation, contribution, reimbursement, indemnification or other rights
      of payment or recovery from any person (including without limitation
      Platinum Re UK) for any payments made by Platinum Holdings hereunder, and
      Platinum Holdings hereby waives and releases, absolutely and
      unconditionally, any such rights of subrogation, contribution,
      reimbursement, indemnification and other rights of recovery that it may
      now have or hereafter acquire.

<PAGE>
                                       6

9.    ASSIGNMENT

      Neither Party may assign its rights under this Agreement without the prior
      written consent of the other. Subject to the foregoing, this Agreement
      shall be binding upon, inure to the benefit of and be enforceable by the
      parties and their respective successors and assigns.

10.   SEVERABILITY

      If any provision of this Agreement or any part of any such provision is
      held to be invalid, unlawful or unenforceable, such provision or part (as
      the case may be) shall be ineffective only to the extent of such
      invalidity, unlawfulness or unenforceability, without rendering invalid,
      unlawful or unenforceable or otherwise prejudicing or affecting the
      remainder of such provision or any other provision of this Agreement.

11.   ENTIRE AGREEMENT

      This Agreement constitutes the whole and only agreement between the
      parties in relation to the subject matter of this Agreement and, save to
      the extent repeated in this Agreement, supersedes any previous agreement
      between the parties with respect thereto.

12.   NO PARTNERSHIP

      Nothing in this agreement and no action taken by the parties under this
      Agreement shall constitute a partnership, association, joint venture or
      other co-operative entity between the parties, nor are the terms of this
      Agreement intended to constitute the parties a joint employer for any
      purpose.

13.   NOTICES

13.1  Any notice required or permitted to be given under this Agreement shall be
      given in writing to the other party at its address set out below:

      if to Platinum Holdings, to:

      Platinum Underwriters Holdings, Ltd.,
      Clarendon House,
      2 Church Street,
      Hamilton HM11
      Bermuda
      Fax number: 441 292 4720
      marked for the attention of the Company Secretary

<PAGE>
                                       7

      if to Platinum Re UK, to:

      Platinum Re (UK) Limited,
      52, Lime Street,
      London, EC3M 7NL
      Fax number: 020 7623 6610
      marked for the attention of the Company Secretary

      or to such other address or fax number, and marked for the attention of
      such other person, as may from time to time be notified by the relevant
      party to the other party.

13.2  Any such notice shall be sent by first class post or facsimile
      transmission (copied by post) or delivered by hand and shall be deemed to
      be served:

      (A)   in the case of post, on the second business day after posting;

      (B)   in the case of facsimile transmission, upon successful transmission
            (or, if the day of sending is not a business day in the place of
            receipt, at the opening of business on the first business day in the
            place of receipt thereafter); and

      (C)   in the case of delivery by hand, upon delivery (or, if the day of
            delivery is not a business day in the place of receipt, at the
            opening of business on the first business day in the place of
            receipt thereafter).

14.   GOVERNING LAW AND JURISDICTION

14.1  This agreement shall be governed by and construed in accordance with
      English law.

14.2  (A)   All disputes and differences arising under or in connection with
            this Agreement shall be referred to arbitration under the
            Arbitration Rules of ARIAS (UK).

      (B)   The Arbitration Tribunal shall consist of three arbitrators, one to
            be appointed by the claimant party, one to be appointed by the
            respondent party and the third to be appointed by the two appointed
            arbitrators.

      (C)   The third member of the Tribunal shall be appointed as soon as
            practicable (and no later than 28 days) after the appointment of the
            two party-appointed arbitrators. The Tribunal shall be constituted
            upon the appointment of the third arbitrator.

      (D)   The Arbitrators shall be persons (including those who have retired)
            with not less than ten years' experience of insurance or reinsurance
            within the industry or as lawyers or other professional advisers
            serving the industry.

      (E)   Where a party fails to appoint an arbitrator within 14 days of being
            called upon to do so or where the two party-appointed arbitrators
            fail to appoint a third within 28 days of their appointment, then
            upon application ARIAS (UK) will appoint an

<PAGE>
                                       8

            arbitrator to fill the vacancy. At any time prior to appointment by
            ARIAS (UK) the party or arbitrators in default may make such
            appointment.

      (F)   The Tribunal may in its sole discretion make such orders and
            directions as it considers to be necessary for the final
            determination of the matters in dispute. The Tribunal shall have the
            widest discretion permitted under the law governing the arbitral
            procedure when making such orders or directions.

      (G)   The seat of arbitration shall be London.

      (H)   Each party shall bear the expense of its own arbitrator, and shall
            jointly and equally bear with the other the expense of the third
            arbitrator and of the arbitration unless otherwise directed by the
            arbitrators.

      (I)   This Clause 14.2 shall survive termination of this Agreement.

15.   COUNTERPARTS

15.1  This Agreement may be executed in any number of counterparts, and by the
      parties on separate counterparts, but shall not be effective until each
      party has executed at least one counterpart.

15.2  Each counterpart shall constitute an original of this Agreement, but the
      counterparts shall together constitute but one and the same instrument.

IN WITNESS of which each of the parties has executed this Agreement on the day
and year first above written.

PLATINUM UNDERWRITERS HOLDINGS, LTD.

By:   /s/ Jerome T. Fadden              Date:

Name: Jerome T. Fadden

Title:

PLATINUM RE (UK) LIMITED

By:     /s/ T.J. MAHONEY                 Date: 31st October, 2002

Name:   T. MAHONEY

Title:  CEO

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