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This announcement is neither an offer to purchase nor a solicitation of an offer
 to sell Shares. The Offer is made solely by the Offer to Purchase, dated July
 17, 2000 (the "Offer to Purchase"), and the related Letter of Transmittal, and
is being made to all holders of Shares. The Offer is not being made to (nor will
tenders be accepted from or on behalf of) holders of Shares in any jurisdiction
   in which the making of the Offer or the acceptance thereof would not be in
 compliance with the securities, blue sky or other laws of such jurisdiction or
 any administrative or judicial action pursuant thereto. In jurisdictions whose
 laws require that the Offer be made by a licensed broker or dealer, the Offer
 shall be deemed to be made on Purchaser's behalf by Credit Suisse First Boston
Corporation ("Credit Suisse First Boston") or Chase Securities Inc. (the "Dealer
 Managers") or by one or more registered brokers or dealers licensed under the
                           laws of such jurisdiction.


                          Notice of Offer to Purchase

                     All Outstanding Shares of Common Stock

                                       of

                      United Asset Management Corporation

                                       at

                              $25.00 Net Per Share

          (subject to adjustment as provided in the Offer to Purchase)

                                       by

                              OM Acquisition Corp.

                          a wholly-owned subsidiary of

                                 Old Mutual plc


     OM Acquisition Corp., a Delaware corporation ("Purchaser") and a
wholly-owned subsidiary of Old Mutual plc, a public limited company incorporated
in England and Wales ("Parent"), is offering to purchase all outstanding shares
of common stock, par value $0.01 per share (the "Shares"), of United Asset
Management Corporation, a Delaware corporation (the "Company"), at a price of
$25.00 per Share, subject to adjustment as provided in the Offer to Purchase,
net to the seller in cash, without interest thereon, upon the terms and subject
to the conditions set forth in the Offer to Purchase, dated July 17, 2000, and
in the related Letter of Transmittal (which, together with any amendments or
supplements thereto, constitute the "Offer"). Tendering stockholders whose
Shares are registered in their name and who tender directly to the Depositary
will not be obligated to pay brokerage fees or commissions or, except as set
forth in Instruction 6 of the Letter of Transmittal, transfer taxes on the
purchase of Shares pursuant to the Offer. The purpose of the Offer is to acquire
for cash as many outstanding Shares as possible as a first step in acquiring the
entire equity interest in the Company. Following consummation of the Offer,
Purchaser intends to effect the merger described below.

 -----------------------------------------------------------------------------
  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
         TIME, ON FRIDAY, AUGUST 11, 2000, UNLESS THE OFFER IS EXTENDED.
 -----------------------------------------------------------------------------

     The Offer is conditioned upon, among other things, there being validly
tendered and not properly withdrawn prior to the expiration of the Offer that
number of Shares which constitutes at least a majority of the Company's then
issued and outstanding Shares of Common Stock on a fully-diluted basis.

     The Offer is being made pursuant to an Agreement and Plan of Merger, dated
as of June 16, 2000 (the "Merger Agreement"), among Parent, Purchaser and the
Company. The Merger Agreement provides, among other things, for the commencement
of the Offer by Purchaser and further provides that after the purchase of Shares
pursuant to the Offer, subject to the satisfaction or waiver of certain
conditions, Purchaser will be merged with and into the Company (the "Merger"),
with the Company surviving the Merger as a wholly-owned subsidiary of Parent. At
the effective time of the Merger, each outstanding Share (other than Shares
owned by the Company or any subsidiary of the Company, and shares owned by
stockholders who have properly exercised their appraisal rights under Delaware
law) will be converted into the right to receive $25.00 per Share, subject to
adjustment as provided in the Offer to Purchase, net to the seller in cash,
without interest thereon.

     The Board of Directors of the Company has unanimously determined that the
Offer and the Merger are fair to, advisable and in the best interests of the
Company and its stockholders, has approved the Offer and the Merger Agreement
and the transactions contemplated thereby, and recommends that the Company's
stockholders accept the Offer and tender all of their Shares pursuant to the
Offer.













     For purposes of the Offer, Purchaser will be deemed to have accepted for
payment, and thereby purchased, Shares validly tendered as, if and when
Purchaser gives oral or written notice to the Depositary (as defined in the
Offer to Purchase) of Purchaser's acceptance of such Shares for payment pursuant
to the Offer. In all cases, upon the terms and subject to the conditions of the
Offer, payment for Shares purchased pursuant to the Offer will be made by
deposit of the purchase price therefor with the Depositary, which will act as
agent for tendering stockholders for the purpose of receiving payment from
Purchaser and transmitting payment to validly tendering stockholders whose
Shares have theretofore been accepted for payment. In all cases, payment for
Shares purchased pursuant to the Offer will be made only after timely receipt by
the Depositary of (i) certificates representing such Shares or a timely
Book-Entry Confirmation (as defined in Section 2 of the Offer to Purchase) with
respect to such Shares and (ii) the Letter of Transmittal (or a facsimile
thereof), properly completed and duly executed, with any required signature
guarantees, or, in the case of a book-entry transfer, an Agent's Message (as
defined in Section 2 of the Offer to Purchase) and (iii) any other documents
required by the Letter of Transmittal. Under no circumstances will interest on
the purchase price for Shares be paid by Purchaser by reason of any delay in
making such payment.

     The term "Expiration Date" means 12:00 midnight, New York City time, on
Friday, August 11, 2000, unless and until Purchaser, in accordance with the
terms of the Offer and the Merger Agreement, shall have extended the period of
time for which the Offer is open, in which event the term "Expiration Date"
shall mean the time and date at which the Offer, as so extended by Purchaser,
shall expire. Purchaser shall not have any obligation to pay interest on the
purchase price for tendered Shares whether or not Purchaser exercises its right
to extend the period of time during which the Offer is open. Any such extension
will be followed by a public announcement thereof by no later than 9:00 a.m.,
New York City time, on the next business day after the previously scheduled
Expiration Date. During any such extension, all Shares previously tendered and
not withdrawn will remain subject to the Offer, subject to the right of a
tendering stockholder to withdraw such stockholder's Shares. Without limiting
the manner in which Purchaser may choose to make any public announcement,
Purchaser shall have no obligation to publish, advertise, or otherwise
communicate any such public announcement other than by issuing a release to the
Dow Jones News Service or as otherwise may be required by law.

     Except as otherwise provided in the Offer to Purchase, tenders of Shares
made pursuant to the Offer are irrevocable. Shares tendered pursuant to the
Offer may be withdrawn at any time prior to the Expiration Date and, unless
theretofore accepted for payment as provided in the Offer to Purchase, may also
be withdrawn at any time after September 14, 2000. For a withdrawal to be
effective, a written or facsimile transmission notice of withdrawal must be
timely received by the Depositary at one of its addresses set forth on the back
cover of the Offer to Purchase. Any such notice of withdrawal must specify the
name, address and taxpayer identification number of the person who tendered the
Shares to be withdrawn, the number of Shares to be withdrawn and the name of
the registered holder, if different from that of the person who tendered such
Shares. If certificates representing Shares have been delivered or otherwise
identified to the Depositary, then prior to the physical release of such
certificates, the tendering stockholder must also submit the serial numbers
shown on the particular certificates evidencing the Shares to be withdrawn, and
the signature on the notice of withdrawal must be guaranteed by an Eligible
Institution, as defined in Section 3 of the Offer to Purchase (except in the
case of Shares tendered for the account of the Eligible Institution). If Shares
have been tendered pursuant to the procedure for book-entry transfer set forth
in Section 3 of the Offer to Purchase, the notice of withdrawal must also
specify the name and number of the account at the Book-Entry Transfer Facility
(as defined in Section 2 of the Offer to Purchase) to be credited with the
withdrawn Shares. All questions as to the form and validity (including time of
receipt) of notices of withdrawal will be determined by Purchaser, in its sole
discretion, whose determination shall be final and binding. Withdrawals of
Shares may not be rescinded. Any Shares properly withdrawn will be deemed not
validly tendered for purposes of the Offer, but may be retendered at any
subsequent time prior to the Expiration Date by following any of the procedures
described in Section 3 of the Offer to Purchase.

     The Company has provided Purchaser with the Company's Stockholder list and
security position listings for the purpose of disseminating the Offer to
holders of Shares. The Offer to Purchase, the related Letter of Transmittal and,
if required, any other relevant materials will be mailed to record holders of
Shares and will be furnished to brokers, dealers, commercial banks, trust
companies and similar persons whose names, or in the name of whose nominees,
appear on the Company's stockholder list or, if applicable, who are listed as
participants in a clearing agency's security position listing, for subsequent
transmittal to beneficial owners of Shares by Purchaser.

     The information required to be disclosed by paragraph (d)(1) of Rule 14d-6
under the Securities Exchange Act of 1934, as amended, is contained in the Offer
to Purchase and is incorporated herein by reference.

     The Offer to Purchase and the related Letter of Transmittal contain
important information which should be read carefully before any decision is made
with respect to the Offer.

     Requests for copies of the Offer to Purchase, Letter of Transmittal and
other tender offer documents may be directed to the Information Agent as set
forth below, and copies will be furnished promptly at Purchaser's expense.
Questions or requests for assistance may be directed to the Information Agent or
the Dealer Managers. Neither Purchaser nor Parent will pay any fees or
commissions to any broker or dealer or other person (other than the Depositary,
the Dealer Managers and the Information Agent) in connection with the
solicitation of tenders of Shares pursuant to the Offer.

                     The Information Agent for the Offer is:

                                [INNISFREE LOGO]

                         501 Madison Avenue, 20th Floor
                            New York, New York 10022
                 Banks and Brokers Call Collect: (212) 750-5833
                   All Others Call Toll-Free: (888) 750-5834

                     The Dealer Managers for the Offer are:

       Credit Suisse First Boston               Chase Securities Inc.
          Eleven Madison Avenue                    270 Park Avenue
      New York, New York 10010-3629            New York, New York 10017
     Call Toll-Free: (800) 881-8320                (212) 270-6383

July 17, 2000

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