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                                                                    Exhibit 4.12

                                AMENDMENT NO. 1
                                       TO
                            STOCK PURCHASE AGREEMENT


     AMENDMENT NO. 1 made this 2d day of August, 2001 to the certain STOCK
PURCHASE AGREEMENT dated April 26, 2001 (the "Agreement") by and between, on the
one hand, AMVESCAP PLC and INVESCO NORTH AMERICAN HOLDINGS, INC. and, on the
other hand, OLD MUTUAL PLC, OLD MUTUAL (US) HOLDINGS INC., AND UNITED ASSET
MANAGEMENT HOLDINGS, INC.

     WHEREAS the parties to the Agreement wish to amend such Agreement as set
forth herein;

     WHEREAS, United Asset Management Holdings, Inc. has been merged with and
into Old Mutual (US) Holdings Inc;

     NOW, THEREFORE, in consideration of the premises, the parties hereto agree
as follows:

     1.  The definition of "Net Tangible Assets" is hereby amended by deleting
the words that appear in clause (ii)(d) thereof and substituting the following
for such deleted words:  "(d) an accrual of $600,000 for the G Family Trust
matter disclosed on revised Schedule 5.11, #54 and an accrual of $62,500 for the
Pelgrin matter disclosed on revised Schedule 5.11, #53, "and a corresponding
reduction in the accrual for incentive compensation under clause (b) above
pursuant to the Revenue Sharing Agreement for the G Family Trust matter."

     2.  The following is hereby added to the definition of "Anniversary Date
Revenue":

          Anniversary Date Revenues for any twelve month period for which such
     revenues are computed shall include revenues received by any Affiliate of
     Purchaser in such period pursuant to any advisory agreement, whether or not
     interim, between such Affiliate of Purchaser and the Mid-Cap Portfolio
     (including any successor thereto).

     3.  The second sentence in Section 2.3(b)(i) of the Agreement is amended to
read as follows:

          With respect to the Mid-Cap Portfolio, the approval by the board of
     directors of UAM Funds, Inc. prior to Closing of an interim advisory
     contract pursuant to Rule 15a-4 of the 1940 Act with an Affiliate of
     Purchaser shall not be
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     deemed to be a termination of the advisory relationship of the Companies
     with the Mid-Cap Portfolio.8

     4.  The Agreement is hereby amended by replacing Section 2.4(b) to read in
its entirety as follows:

          (b) Payment of any amounts payable under this Section 2.4 shall be
       made by wire transfer of immediately available funds either to (i) an
       account of Old Mutual designated in writing delivered to the Buyer or
       (ii) directly to PRCI, on the Sellers' behalf, in accordance with the
       Signing Bonus Plan.

     5.  The Agreement is hereby further amended by replacing the first sentence
of Section 2.7(a) with the following sentence:  "The closing of the transaction
contemplated by this Agreement (the "Closing") shall take place at the offices
                                     -------
of Hill & Barlow, One International Place, Boston, Massachusetts 02110,
commencing at 10:00 a.m. on August 2, 2001."

     6.  Section 3.1(g) of the Agreement is amended to read as follows:

          (g)  Old Mutual shall have obtained  from each holder of a Unit Award
     the executed written agreement of such holder to surrender all Unit Awards
     held by such holder for redemption upon payment to such holder of the
     redemption price therefor (each a "Redemption Agreement" and collectively,
     the "Redemption Agreements"), the originals of all such Redemption
     Agreements shall have been delivered by Old Mutual to Christopher Cabot at
     Sullivan & Worcester ("S&W")  to be delivered to Purchaser as provided in
     Section 4.15 below, and Old Mutual shall have delivered to Purchaser copies
     of each such Redemption Agreement or other evidence reasonably satisfactory
     to Purchaser that all holders of outstanding Unit Awards have agreed to
     surrender the Unit Awards respectively held by such holders for redemption.

     7.  Section 4.12(b) of the Agreement is amended to read in its entirety as
follows:

          (b)  Purchaser agrees that it will, effective from and after the
     Closing, cause Pell Rudman to implement the Restated Pell Rudman Signing
     Bonus Plan (the "Signing Bonus Plan") in the form of Exhibit A to this
                                                          ---------
     Amendment No. 1.  Parent and Old Mutual shall be solely responsible for
     paying, and shall pay in accordance with Pell Rudman's

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     direction, as and when due in accordance with and subject to the terms of
     the Signing Bonus Plan, to Pell Rudman (or at Pell Rudman's further
     direction, to Purchaser or an Affiliate of Purchaser that will make payment
     of the bonus amounts payable under the Signing Bonus Plan) all amounts that
     are or become payable by Parent and Old Mutual under the Signing Bonus Plan
     (including, without limitation, the Aggregate Closing Date Bonus Pool, as
     such term is defined in the Signing Bonus Plan), it being understood that
     any payments so made by Parent and Old Mutual shall not be deemed a
     reduction in or return of the Purchase Price payable hereunder for
     financial accounting purposes and that all such payments shall be deemed
     made to and for the benefit of Pell Rudman under the terms of and in
     accordance with the Signing Bonus Plan. Purchaser (or its Affiliate) will,
     as soon as practical following its receipt of such payments, and acting
     solely in the capacity of a payroll paying agent for Pell Rudman and as an
     accommodation to Parent, Old Mutual and Pell Rudman, make payment to the
     participants in the Signing Bonus Plan of the Closing Date Bonuses;
     provided, however, that subject to receipt by Purchaser on or before August
     7, 2001 of the Aggregate Closing Date Bonus Pool in immediately available
     funds and the receipt by Purchaser prior to August 2, 2001 of satisfactory
     payroll payment information in electronic form compatible with Purchaser's
     payroll payment systems with respect to all participants who are to receive
     Closing Date Bonus payments, Purchaser shall cause the Closing Date Bonuses
     to be paid on August 8, 2001.

     8.  Section 4.15 of the Agreement is amended to read as follows:

          4.15 Redemption of Unit Awards.  On the Closing Date, Old Mutual will
               -------------------------
     cause its counsel to deliver to Christopher Cabot at S&W, the original of
     each executed Redemption Agreement and shall pay to Pell Rudman, by wire
     transfer to an account designated by Pell Rudman, an amount equal to the
     aggregate amount payable, plus the aggregate amount of the employers'
     portion of any FICA, Medicare, Social Security or other like taxes with
     respect to such payments, under all such Redemption Agreements in
     redemption of all Unit Awards.  Pursuant to a separate Letter Agreement,
     S&W has agreed to deliver all such Redemption Agreements to Pell Rudman
     promptly upon receipt of notice of payment by Pell Rudman of the amounts
     payable thereunder.  Not later than August 5, 2001, Old Mutual will deliver
     to Purchaser such information as Purchaser shall reasonably require in

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     order to pay the amounts payable under the Redemption Agreements.  On
     August 15, 2001, and subject to the contemporaneous delivery of all such
     Redemption Agreements and the timely receipt of the payment information
     described in the foregoing sentence, Purchaser, as agent for Pell Rudman,
     shall pay to each holder of a Unit Award or Unit Awards the amount payable
     to such holder under and in respect of the Redemption Agreement
     respectively executed by such holder, all such Redemption Agreements shall
     be deemed delivered and effective, and all such Unit Awards shall thereupon
     be deemed redeemed and no longer issued or outstanding.

     9.  Article IV of the Agreement is amended by adding thereto Section 4.18,
which shall read in its entirety as follows:

     4.18  Mid-Cap Portfolio.  Purchaser and Parent covenant that they will use
           -----------------
          all commercially reasonable efforts to assure that an affiliate of
          Purchaser maintains a fee-generating advisory relationship with the
          Mid-Cap Portfolio through the Second Anniversary Date.

     10.  Section 9.2 (a)(i) of the Agreement is amended by inserting
immediately following the words "Section 5.19" the following language: "or Item
                                 ------------
7 of Schedule 5.7."
     ------------

     11.  Section 9.2(a) of the Agreement is amended further by deleting the
word "or" at the end of clause (iii) thereof, replacing the "." at the end of
clause (iv) thereof with ";" and adding the following:

     "(v) the Pelgrin matter referred to in revised Schedule 5.11, #53 and the G
     Family Trust matter referred to in revised Schedule 5.11, #54 (but in each
     case only to the extent the aggregate Loss with respect to such matters
     exceed any amount paid or accrued and reflected in the computation of
     Actual Net Tangible Assets).

     12.  All other provisions of the Agreement are unchanged.

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1 to
be executed as of the date first written above.

                       [SIGNATURES CONTINUE ON NEXT PAGE]

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         [SIGNATURE PAGE TO AMENDMENT NO. 1 TO STOCK PURCHASE AGREEMENT]

                         AMVESCAP PLC

                         By: /s/ Robert F. McCullough
                            ---------------------------------
                            Title: CFO


                         INVESCO NORTH AMERICAN HOLDINGS, INC.

                         By: /s/ Neil Williams
                            ---------------------------------
                            Title: General Counsel & Secretary



                         OLD MUTUAL (US) HOLDINGS INC.

                         By: /s/ Franklin H. Kettle
                            ---------------------------------
                            Title:

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