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                                                                    EXHIBIT 10.2

                                  GECS/CAN.22.1

                                17 September 1999

                       Supplemental investment agreement

                       between

                       Inveresk Research Group Limited

                       Walter Nimmo and others

                       and

                       Candover Investments PLC and others
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THIS AGREEMENT IS MADE ON 17 SEPTEMBER 1999

between

(1)   INVERESK RESEARCH GROUP LIMITED (registered number 198206) having its
      registered office at Elphinstone Research Centre, Tranent, Edinburgh EH33
      2NE ("Newco");

(2)   THE PERSONS whose names are set out in Schedule 1 (together the
      "Directors" and each a "Director"); and

(3)   THE PERSONS whose names and addresses are set out in Schedule 2 (together
      the "Investors" and each an "Investor")

WHEREAS

(A)   Pursuant to an investment agreement dated 4 September 1999 (the
      "Investment Agreement") the Directors and the Investors agreed to invest
      in Newco for the purposes of and subject to the terms and conditions of
      the Investment Agreement.

(B)   The parties have agreed to enter into this Agreement which is
      supplementary to the Investment Agreement.

IT IS HEREBY AGREED as follows:

1.          Interpretation

1.1         Unless the context otherwise requires, expressions defined in the
            Investment Agreement shall have the same meaning in this Agreement.

1.2         Reference to "Recitals", "Clauses" and "Schedules" and to
            sub-divisions thereof are to recitals and clauses of and the
            schedules to this Agreement and sub-divisions thereof. The Schedules
            shall form part of this Agreement.

1.3         The headings in this Agreement are for convenience only and shall
            not affect its construction or interpretation.

1.4         Unless the context otherwise requires:

1.4.1       words denoting the singular shall include the plural and vice versa;

1.4.2       words denoting a gender shall include all genders; and

1.4.3       references to persons shall include natural persons, bodies
            corporate, unincorporated associations, partnerships, joint
            ventures, trusts or other entities or organisations of any kind,
            including (without limitation) government entities (or political
            subdivisions or agencies or instrumentalities thereof).
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                                        2

2.       Investor protection

2.1      Newco hereby agrees with and undertakes to the Investors that it shall,
         so far as within its power, not permit any act or omission to occur
         between the execution of this Agreement and Completion which would
         require the consent of the Investors under the Agreement or the consent
         of holders of A Ordinary Shares under the Articles if the Articles had
         been adopted at the date of this Agreement.

2.2      Each of Messrs Nimmo and Leslie hereby agrees with and undertakes to
         the Investors that he shall, so far as within his power, not permit any
         act or omission to occur between the execution of this Agreement and
         Completion which would require the consent of the Investors under the
         Agreement or the consent of holders of A Ordinary Shares under the
         Articles if the Articles had been adopted at the date of this Agreement
         without first consulting the Investors provided that no consent of the
         Investors or the holders of A Ordinary Shares shall be required in
         connection with any such act or omission.

3.       Amendment of Investment Agreement

         The Investment Agreement shall be amended:

3.1      by the addition to Schedule 3 of the Agreement of the following as a
         new paragraph 9:

         "9.      There having been no breach of clause 2 of the supplemental
                  subscription agreement dated 17 September 1999 between the
                  parties thereto." and

3.2      by the addition to Schedule 4 of the Agreement of the following
         additional warranties:

         "7.      So far as the Warrantors are aware, since execution of the
                  supplemental subscription agreement dated 17 September 1999
                  between the parties thereto:

         7.1      Newco has not undertaken any trading and has not incurred any
                  new liabilities of any nature whatsoever whether actual or
                  contingent;

         7.2      Newco has not become engaged in and is not about to initiate
                  any litigation or arbitration and, so far as the Directors are
                  aware, no such litigation or arbitration is pending or
                  threatened against Newco;

         7.3      Newco has not taken any corporate action nor have any steps
                  been taken or legal proceedings been started or threatened
                  against it for winding up, dissolution or reorganisation or
                  for the appointment of a receiver or administrative receiver
                  or any administrator, trustee or similar officer of it or of
                  any of its assets or revenues;

         7.4      No mortgages, charges, liens, encumbrances or other security
                  interests (save for liens and retentions of title arising
                  automatically by operation of law or in the ordinary and usual
                  course of business) subsist over the undertaking or assets of
                  Newco;
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                                        3

         7.5      None of the directors of Newco has been given any service
                  contract with Newco or any member of the Group other than the
                  Directors' Service Contracts;

         7.6      No options have been granted or agreements entered into which
                  call for the issue of or accord to any person the right to
                  call for the issue of any shares in the capital of Newco; and

         7.7      Newco has not had (and will not following completion of the
                  transactions envisaged in this Agreement have) any interest in
                  the shares of any company other than the Targets."

3.3      by the addition to Schedule 4 at the end of the paragraph commencing
         with the words "The Warranties in this Schedule 4" the following:

         "... and the Warranties contained in paragraph 7 shall be deemed to be
         given by each of Stewart Leslie and Walter Nimmo only."

4.       Fees and expenses

         All legal and accountancy fees (plus any expenses and VAT) of the
         Investors in relation to this Agreement shall be for the account of
         Newco and shall be payable on the date of completion of the Investment
         Agreement.

5.       Counterparts

         This Agreement may be executed in any number of counterparts by the
         different parties hereto on separate counterparts, each of which when
         executed and delivered shall constitute an original, but all of which
         shall together constitute one and the same instrument.

6.       Applicable Law

         This Agreement shall be governed by and construed in accordance with
         English law and all the parties hereto irrevocably submit to the
         non-exclusive jurisdiction of the High Court in London as regards any
         claim, dispute or matter arising out of or relating to this Agreement
         or any of the documents to be executed pursuant to it.

AS WITNESS WHEREOF this Agreement has been executed on the date first above
written.
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                                       4


                                   Schedule 1

                                  The Directors

Walter Nimmo

Ian Sword

Stewart Leslie
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                                       5


                                   Schedule 2

                                  The Investors

Name & Address

Candover Investments PLC
20 Old Bailey
London EC4M 7LN

Candover Trustees Limited
20 Old Bailey
London EC4M 7LN

Candover 1997 UK Limited
Partnership, 20 Old Bailey,
London EC4M 7LN acting by
their general partner
Candover Partners Limited

Candover 1997 UK No 2 Limited
Partnership, 20 Old Bailey,
London EC4M 7LN acting by
their general partner Candover
Partners Limited

Candover 1997 US No 1 Limited
Partnership, 20 Old Bailey,
London EC4M 7LN acting by
their general partner Candover
Partners Limited

Candover 1997 US No 2 Limited
Partnership, 20 Old Bailey,
London EC4M 7LN acting by
their general partner Candover
Partners Limited

Candover 1997 US No 3 Limited
Partnership)20 Old Bailey, London
EC4M 7LN acting by their general
partner Candover Partners Limited
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Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Inveresk Research Group Limited                      )  ........................
acting by Marek Gumienny, director,                  )  Director
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................
            Susan Coughlan
Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London EC2V6HR
            .......................................

Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Candover Investments PLC                             )  ........................
acting by Marek Gumienny, director,                  )  Director
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................

Witness     .......................................

Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London EC2V6HR
            .......................................

Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Candover Trustees Limited                            )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................

Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London EC2V6HR
            .......................................
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                                       7


Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Candover 1997 UK Limited Partnership                 )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................
            Susan Coughlan
Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London ECZ V 6HR
            .......................................

Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Candover 1997 UK No 2 Limited Partnership            )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................
            Susan Coughlan
Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London ECZ V 6HR
            .......................................

Signed as a deed for and on behalf of                )  /s/ Marek Gumienny
Candover 1997 US No 1 Limited Partnership            )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

            /s/ Susan Coughlan
Witness     .......................................
            Susan Coughlan
Full Name   .......................................
            Maclays
Address     .......................................
            10 Foster Lane
            .......................................
            London ECZ V 6HR
            .......................................
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                                       8


Signed as a deed for and on behalf of                )   /s/ Marek Gumienny
Candover 1997 US No 2 Limited Partnership            )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

             /s/ Susan Coughlan
Witness     .......................................
              Susan Coughlan
Full Name   .......................................
              Maclays
Address     .......................................
              10 Foster Lane
            .......................................
              London ECZ V6HR
            .......................................

Signed as a deed for and on behalf of                )   /s/ Marek Gumienny
Candover 1997 US No 3 Limited Partnership            )  ........................
acting by Marek Gumienny as their attorney           )  Attorney
in the presence of this witness:                     )

             /s/ Susan Coughlan
Witness     .......................................
              Susan Coughlan
Full Name   .......................................
              Maclays
Address     .......................................
              10 Foster Lane
            .......................................
              London ECZ V6HR
            .......................................
                                                         /s/ Walter Nimmo
Signed as a deed by Walter Nimmo                     )  ........................
in the presence of this witness:                     )  Walter Nimmo

             /s/ Catherine Mary Christie
Witness     .......................................

Full Name   .......................................

Address     .......................................

            .......................................

            .......................................


                                                        /s/ Ian Sword
Signed as a deed by Ian Sword                        )  ........................
in the presence of this witness:                     )  Ian Sword

            /s/ Margaret Hay
Witness     .......................................
            Margaret Hay
Full Name   .......................................

Address     .......................................

            .......................................

            .......................................

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<TABLE>
<CAPTION>
Contents                                                                    Page
--------                                                                    ----
<S>                                                                         <C>
1.          Interpretation                                                     1

2.          Investor protection                                                2

3.          Amendment of Investment Agreement                                  2

4.          Fees and expenses                                                  2

5.          Counterparts                                                       2

6.          Applicable law                                                     2
</TABLE>

Schedules

Schedule 1  The Directors

Schedule 2  The Investors