This announcement is neither an offer to purchase nor a solicitation
of an offer to sell Shares (as defined below). The Offer (as defined below)
is being made solely by the Offer to Purchase dated June 14, 2000 and the
related Letter of Transmittal, and is being made to all holders of Shares.
Purchaser (as defined below) is not aware of any jurisdiction where the
making of the Offer is prohibited by any administrative or judicial action
pursuant to any valid state statute. If Purchaser becomes aware of any valid
state statute prohibiting the making of the Offer or the acceptance of Shares
pursuant thereto, Purchaser will make a good faith effort to comply with such
state statute. If, after such good faith effort, Purchaser cannot comply with
such state statute, the Offer will not be made to (nor will tenders be
accepted from or on behalf of) the holders of Shares in such state. In any
jurisdiction where the securities, blue sky or other laws require the Offer
to be made by a licensed broker or dealer, the Offer shall be deemed to be
made on behalf of Purchaser by Morgan Stanley & Co. Incorporated or one or
more registered brokers or dealers licensed under the laws of such
jurisdiction.

                      NOTICE OF OFFER TO PURCHASE FOR CASH

                     ALL OUTSTANDING SHARES OF COMMON STOCK
             (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)

                                       OF

                               PRIMARK CORPORATION

                                       AT

                              $38.00 NET PER SHARE

                                       BY

                         MARQUEE ACQUISITION CORPORATION

                     AN INDIRECT WHOLLY OWNED SUBSIDIARY OF

                             THE THOMSON CORPORATION

         Marquee Acquisition Corporation, a Michigan corporation (the
"PURCHASER") and an indirect wholly owned subsidiary of The Thomson
Corporation, a corporation organized under the laws of Ontario, Canada
("PARENT"), is offering to purchase all the issued and outstanding shares of
Common Stock, no par value per share (the "COMMON STOCK") (including, without
limitation, all shares issuable upon the conversion of any convertible
security or upon the exercise of any options, warrants or rights (other than
the rights issued pursuant to the Rights Agreement, dated as of May 29, 1997,
between the Company (as defined herein) and BankBoston, N.A. as rights agent)
(hereinafter, the "RIGHTS") (the Common Stock and the Rights, collectively,
the "SHARES"), of Primark Corporation, a Michigan corporation (the
"COMPANY"), for $38.00 per Share, net to the seller in cash, upon the terms
and subject to the conditions set forth in the Offer to Purchase, dated June
14, 2000 (the "OFFER TO PURCHASE"), and in the related Letter of Transmittal
(which, together with the Offer to Purchase and any amendments or supplements
thereto, collectively constitute the "OFFER"). Following the Offer, Purchaser
intends to effect the Merger (as defined below).

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

         The Offer is conditioned upon, among other things, (i) there having
been validly tendered and not withdrawn prior to the expiration of the Offer at
least the number of Shares that shall constitute fifty-one percent (51%) of the
then outstanding Shares on a fully diluted basis and (ii) any applicable waiting
period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
amended, and any applicable antitrust acts of any other jurisdiction, including
the United Kingdom and the Federal Republic of Germany, having expired or been
terminated prior to the expiration of the Offer.



                                       2


         The Offer is being made pursuant to an Agreement and Plan of Merger,
dated as of June 5, 2000 (the "MERGER AGREEMENT"), among Parent, Purchaser
and the Company. The Merger Agreement provides, among other things, that as
promptly as practicable after the purchase of Shares pursuant to the Offer
and the satisfaction or, if permissible, waiver of the other conditions set
forth in the Merger Agreement and in accordance with the relevant provisions
of the Michigan Business Corporation Act ("MICHIGAN LAW"), Purchaser will be
merged with and into the Company (the "MERGER"). As a result of the Merger,
the Company will continue as the surviving corporation (the "SURVIVING
CORPORATION") and will become an indirect wholly owned subsidiary of Parent.
At the effective time of the Merger (the "EFFECTIVE TIME") and without any
action on the part of the holder thereof, each Share issued and outstanding
immediately prior to the Effective Time (other than Shares held in the
treasury of the Company or Shares held by Parent, Purchaser or any subsidiary
of Parent or of the Company, and other than Shares held by shareholders who
shall have demanded and perfected appraisal rights under Michigan Law, if
any) will be converted into the right to receive $38.00 net in cash, or any
higher price that may be paid per Share in the Offer, without interest.

         THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY DETERMINED
THAT THE MERGER AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY,
INCLUDING THE OFFER AND THE MERGER, ARE FAIR TO, AND IN THE BEST INTERESTS
OF, THE HOLDERS OF THE SHARES, AND HAS APPROVED AND ADOPTED THE MERGER
AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY, INCLUDING EACH OF THE
OFFER AND THE MERGER, AND HAS RECOMMENDED THAT THE HOLDERS OF SHARES ACCEPT
THE OFFER AND TENDER 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 and not properly
withdrawn as, if and when Purchaser gives oral or written notice to ChaseMellon
Shareholder Services, L.L.C. (the "Depositary") of Purchaser's acceptance for
payment of such Shares pursuant to the Offer. Upon the terms and subject to the
conditions of the Offer, payment for Shares accepted for payment pursuant to the
Offer will be made by deposit of the purchase price therefor with the
Depositary, which will act as agent for tendering shareholders for the purpose
of receiving payments from Purchaser and transmitting such payments to tendering
shareholders whose Shares have been accepted for payment. UNDER NO CIRCUMSTANCES
WILL INTEREST ON THE PURCHASE PRICE FOR SHARES BE PAID, REGARDLESS OF ANY DELAY
IN MAKING SUCH PAYMENT. In all cases, payment for Shares tendered and accepted
for payment pursuant to the Offer will be made only after timely receipt by the
Depositary of (i) the certificates evidencing such Shares (the "SHARE
CERTIFICATES") or timely confirmation of a book-entry transfer of such Shares
into the Depositary's account at the Book-Entry Transfer Facility (as defined in
Section 2 of the Offer to Purchase) pursuant to the procedure set forth in
Section 3 of the Offer to Purchase, (ii) the Letter of Transmittal (or a
manually signed facsimile thereof), properly completed and duly executed, with
any required signature guarantees or an Agent's Message (as defined in Section 2
of the Offer to Purchase) and (iii) any other documents required under the
Letter of Transmittal.

         Purchaser expressly reserves the right, in its sole discretion (but
subject to the terms and conditions of the Merger Agreement), at any time and
from time to time, to extend for any reason the period of time during which the
Offer is open, including the occurrence of any condition specified in Section 14
of the Offer to Purchase, by giving oral or written notice of such extension to
the Depositary. Any such extension will be followed as promptly as practicable
by public announcement thereof, such announcement to be made no later than 9:00
a.m., New York City time, on the next business day after the previously
scheduled expiration date of the Offer. During any such extension, all Shares
previously tendered and not withdrawn will remain subject to the Offer and
subject to the right of a tendering shareholder to withdraw such shareholder's
Shares.

         Shares may be withdrawn at any time prior to 12:00 Midnight, New York
City time, on July 12, 2000 (or the latest time and date at which the
Offer, if extended by Purchaser, shall expire). For the 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 page of the Offer to Purchase. Any such notice of withdrawal must specify
the name of the person who tendered the Shares to be withdrawn, the number of
Shares to be withdrawn and the name of the registered holder of such Shares, if
different from that of the person who tendered such Shares. If Share
Certificates evidencing Shares to be withdrawn have been delivered or otherwise
identified to the Depositary, then, prior to the physical release of such Share
Certificates, the serial numbers shown on such Share Certificates must be
submitted to the Depositary and the signature(s) on the notice of withdrawal
must be guaranteed by an Eligible Institution (as defined in Section 3 of the
Offer to Purchase), unless such Shares have been tendered



                                       3


for the account of an Eligible Institution. If Shares have been tendered
pursuant to the procedure for book-entry transfer as set forth in Section 3 of
the Offer to Purchase, any notice of withdrawal must specify the name and number
of the account at the Book-Entry Transfer Facility to be credited with the
withdrawn Shares. All questions as to the form and validity (including the time
of receipt) of any notice of withdrawal will be determined by Purchaser, in its
sole discretion, which determination will be final and binding.

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

         The Company has provided Purchaser with the Company's shareholder list
and security position listings, including the most recent list of names,
addresses and security positions of non-objecting beneficial owners in the
possession of the Company, for the purpose of disseminating the Offer to holders
of Shares. The Offer to Purchase and the related Letter of Transmittal will be
mailed to record holders of Shares whose names appear on the Company's
shareholder lists and will be furnished, for subsequent transmittal to
beneficial owners of Shares, to brokers, dealers, commercial banks, trust
companies and similar persons whose names, or the names of whose nominees,
appear on the shareholder list or, if applicable, who are listed as participants
in a clearing agency's security position listing.

         THE OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.

         Questions and requests for assistance or for additional copies of the
Offer to Purchase and the related Letter of Transmittal and other tender offer
materials may be directed to the Information Agent or the Dealer Manager as set
forth below, and copies will be furnished promptly at Purchaser's expense. No
fees or commissions will be paid to brokers, dealers or other persons (other
than the Information Agent, the Dealer Manager and the Depositary) for
soliciting tenders of Shares pursuant to the Offer.

                     The Information Agent for the Offer is:

                           INNISFREE M&A INCORPORATED

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

                      The Dealer Manager for the Offer is:

                           MORGAN STANLEY DEAN WITTER

                        Morgan Stanley & Co. Incorporated
                                 1585 Broadway,
                               New York, NY 10036
                                 (212) 761-6051


JUNE 14, 2000