Announcement








                  Company Celltech Group PLC
                  TIDMCCH
                  Headline Offer for Oxford GlycoScience
                  Released 07:01 26 Feb 2003
                  Number 9807H






NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO AUSTRALIA, CANADA OR
JAPAN

26 February 2003
CELLTECH GROUP PLC ("CELLTECH")
CASH OFFER FOR OXFORD GLYCOSCIENCES PLC ("OGS")
Summary:
  The board of Celltech announces the terms of a cash offer for the entire
  issued, and to be issued, share capital of OGS.

  The Offer will be 182 pence in cash for each OGS Share, valuing the entire
  issued share capital of OGS at approximately GBP101.4 million.

  The Offer is substantially earnings and cash neutral for Celltech.

Rationale for the Offer:

  Celltech believes that its cash offer represents an opportunity to acquire
  important tangible and intangible assets that it can harness into its
  extensive R&D capabilities.

  Celltech believes that, using its various antibody and small molecule
  technology platforms, it has the ability to exploit certain novel protein
  disease targets identified and patented by OGS. In addition, Celltech
  believes that the integration of OGS' bio-informatics capabilities will
  expand its own capabilities in this area. Zavesca, OGS' licensed product
  for the treatment of mild to moderate Type I Gaucher disease, will generate
  a future income stream that will be of value to Celltech.

  Further, Celltech believes that its cash offer represents a significant
  premium to the value of Cambridge Antibody Technology Group plc's ("CAT")
  share offer, announced on 23 January 2003. The proposed transaction between
  CAT and OGS valued each OGS share at 148.5 pence as at the close of business
  on 25 February 2003. This equates to a valuation for OGS of GBP82.8 million
  against a value of OGS on 22 January 2003 (the last UK Business Day before
  the announcement by CAT and OGS of their agreed merger) of GBP85.0 million.

  Celltech has previously indicated to its shareholders that, since its
  existing business is cash generative, it does not need to raise funds for
  existing operations or for small product or technology acquisitions. In
  keeping with this philosophy, and to avoid any dilution for its existing
  shareholders,   Celltech is offering cash for each OGS share, funded from
  its existing cash resources and credit facilities.

The Offer represents:

  An additional 29.5p per OGS Share, equivalent to a premium of approximately
  19.3 per cent. over 152.5p, being the Closing Price of an OGS Share on 22
  January 2003, the last UK Business Day prior to the announcement by CAT and
  OGS of their agreed merger.

  An additional 35p per OGS Share, equivalent to a premium of approximately
  23.8 per cent. over 147p, being the 10-day volume weighted average trading
  price of an OGS Share on 22 January 2003, the last UK Business Day prior to
  the announcement by CAT and OGS of their agreed merger.

  An additional 33.5p per OGS Share, equivalent to a premium of approximately
  22.6 per cent. over 148.5p, being the implied value of an OGS Share under
  the CAT merger offer on 25 February 2003, the last UK Business Day prior to
  the announcement by Celltech of the Offer.

Financial effects on Celltech:

  Celltech plans to undertake a rapid integration of OGS, which is expected
  to be substantially complete in the second half of 2003. The financial
  impact on Celltech's earnings profile is anticipated to be negligible.

 Dr Peter Fellner, Chief Executive of Celltech, commented:

"We believe that Celltech is well placed to extract value from the
  acquisition of OGS due to the complementarity of activities, Celltech's
  management experience and its successful track record in integrating
  acquisitions. This represents a cash neutral acquisition of important
  assets for Celltech. Our integration plans are being formulated and we
  anticipate   minimal impact on Celltech's operating earnings."

This summary should be read in conjunction with the full text of the
following announcement about the Offer.

There will be a presentation to analysts at 09:30 a.m. today in the Great
Hall at JPMorgan, 60 Victoria Embankment, London, EC4Y 0JP. A live webcast
of this presentation will be available on www.celltechgroup.com, with a
replay facility available for approximately 30 business days thereafter.

Enquiries:
For further information contact:

Celltech Group plc Telephone: +44 (0)1753 534 655

Dr Peter Fellner, Chief Executive

Peter Allen, Chief Financial Officer

Richard Bungay, Director of Corporate Communications

JPMorgan Telephone: +44 (0)20 7742 4000

Bernard Taylor, Vice Chairman

Julian Oakley, Managing Director

Brunswick London

Jon Coles Telephone: +44 (0)20 7404 5959
Fiona Fong

Brunswick New York

Cindy Leggett-Flynn Telephone: +1 212 333 3810

This announcement does not constitute an offer or invitation to purchase
any securities or a solicitation of an offer to buy any securities, pursuant
to the Offer or otherwise. The Offer will be made solely by the Offer
Document and the Acceptance Forms accompanying the Offer Document, which will
contain the full terms and conditions of the Offer, including details of how
the Offer may be accepted. Celltech will be filing a Tender Offer Statement
containing the Offer Document and other related information on the date the
Offer Document is mailed to OGS Securityholders. Free copies of those
documents will be available on the SEC's website at www.sec.gov.

The Offer Document and the Acceptance Forms
accompanying the Offer Document will be made available to all OGS
Securityholders at no charge to them. OGS Securityholders are advised to
read the Offer Document and the accompanying Acceptance Forms when they are
sent to them because they will contain important information. OGS
Securityholders in the US are also advised to read the Tender Offer Statement
because it will contain important information.

Unless otherwise determined by Celltech and permitted by applicable law and
regulation, the Offer (including the Loan Note Alternative) will not be made,
directly or indirectly, in or into, or by use of the mails of, or by any
other means or instrumentality (including, without limitation, telephonically
or electronically) of interstate or foreign commerce of, or of any facility
of a national securities exchange of Canada, nor will it be made in or into
Australia or Japan and the Offer will not be capable of acceptance by any
a orJapan. Accordingly, unless otherwise determined by Celltech and
permitted by applicable law and regulation, neither copies of this
announcement nor any
other documents relating to the Offer are being, or may be, mailed or
otherwise forwarded, distributed or sent in or into Australia, Canada or
Japan and persons receiving such documents (including custodians, nominees
and trustees) must not distribute or send them in, into or from such
jurisdictions.

The Loan Notes to be issued pursuant to the Loan Note Alternative have not
been, and will not be, listed on any stock exchange and have not been and
will not be registered under the US Securities Act or under any relevant
securities laws of any state or other jurisdiction of the United States, or
under the relevant securities laws of Australia, Canada or Japan or any other
 jurisdiction. Accordingly, unless an exemption under such relevant laws is
available, Loan Notes may not be offered, sold, re-sold or delivered, directly
or indirectly, in, into or from the United States, Australia, Canada or Japan
or any other jurisdiction in which an offer of Loan Notes would constitute a
violation of relevant laws or require registration of the Loan Notes, or to or
for the account or benefit of any US Person or resident of Australia, Canada
or Japan or any other such jurisdiction.

JPMorgan is acting for Celltech and for no one else in connection with the
Offer and will not be responsible to anyone other than Celltech for providing
the protections afforded to customers of JPMorgan or for providing advice in
relation to the Offer.

The Panel wishes to draw the attention of member firms of NASDAQ to certain
UK dealing disclosure requirements during the offer period. The offer period
(in accordance with the City Code, which is published and administered by the
Panel) commences at the time when an announcement is made of a proposed or
possible offer, with or without terms. OGS has equity securities traded on the
London Stock Exchange and NASDAQ.

The above disclosure requirements are set out in more detail in Rule 8 of the
City Code. In particular, Rule 8 requires public disclosure of dealings during
the offer period by persons who own or control, or who would as a result of
any transaction own or control, one per cent. or more of any class of relevant
securities of the offeree company. Relevant securities include OGS Shares, OGS
ADSs and instruments convertible into OGS Shares or OGS ADSs. This requirement
will apply until the first closing date or, if this is later, the date when
the Offer becomes or is declared unconditional or lapses.

Disclosure should be made on an appropriate form by no later than 12 noon
London time (7 a.m. New York City time) on the business day following the date
of the dealing transaction. These disclosures should be published through a
Regulatory Information Service.

The Panel requests that member firms advise those of their clients who wish to
deal in the relevant securities of OGS, whether in the United States or in the
UK, that they may be affected by these requirements. If there is any doubt as
to their application the Panel should be consulted (telephone number: +44 (0)
20 7382 9026, fax number: +44 (0) 20 7638 1554).

This announcement contains certain "forward-looking" statements which are
naturally subject to uncertainty and changes in circumstances. Actual results
may vary materially from the expectations contained in this announcement. The
forward-looking statements contained in this announcement include statements
about the feasibility and benefits of the acquisition of OGS by Celltech.
Factors that would cause actual results to differ materially from those
described in this announcement include: the inability to obtain necessary
regulatory approvals or to obtain them on acceptable terms; the inability
successfully to integrate OGS within the Celltech Group or to realise
synergies from such integration; costs related to the acquisition of OGS;
the economic environment of the industries in which Celltech and OGS operate;
the general economic environment; and other risk factors detailed in OGS' and
Celltech's filings with the SEC.

This announcement has been approved by JPMorgan for the purpose of section 21
of the Financial Services and Markets Act 2000 only.

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO AUSTRALIA, CANADA OR
JAPAN

26 February 2003

CELLTECH GROUP PLC ("CELLTECH")

CASH OFFER FOR OXFORD GLYCOSCIENCES PLC ("OGS")

1.Introduction

  The board of Celltech announces the terms of a cash offer for the entire
  issued, and to be issued, share capital of OGS. The Offer is to be made
  by Celltech and (outside the United States) JPMorgan on its behalf and is
  subject to the applicable requirements of the City Code and US federal
  securities laws, subject to customary exemptions granted by the SEC in
  relation to the Offer.

  The Offer will be 182 pence in cash for each OGS Share, valuing the entire
  issued share capital of OGS at approximately GBP101.4 million.

2.The Offer

  The Offer, which will be subject to the conditions and further terms set
  out in Appendix I and to be set out in the Offer Document and Acceptance
  Forms, will be made on the following basis:

  for each OGS Share (including those represented by OGS ADSs) 182 pence in
  cash.

  This represents 182 pence in cash per OGS ADS (each OGS ADS
  representing one OGS Share).

  The OGS Shares (including those represented by OGS ADSs) which are the
  subject of the Offer will be acquired by Celltech pursuant to the Offer
  fully paid and free from all liens, charges, equitable interests, third
  party rights and interests and encumbrances and together with all rights
  now or hereafter attaching thereto, including the right to receive all
  dividends and other distributions (if any) declared, made or paid after
  the date of this announcement.

  The Offer extends to any OGS Shares (including those represented by OGS
  ADSs) which are unconditionally allotted or issued prior to the date on
  which the Offer closes (or such earlier date, not being earlier than the
  date on which the Offer becomes or is declared wholly unconditional, as
  Celltech may, subject to the City Code, decide) as a result of the
  exercise of options or rights granted under the OGS Share Option Schemes
  or otherwise.

3.Premium

  The Offer represents:

  an additional 29.5p per OGS Share, equivalent to a premium of
  approximately 19.3 per cent. over 152.5p, being the Closing Price of an
  OGS Share on 22 January 2003, the last UK Business Day prior to the
  announcement by Cambridge Antibody Technology Group plc ("CAT") and OGS
  of their agreed merger

  an additional 35.0p per OGS Share, equivalent to
  a premium of approximately 23.8 per cent. over 147p, being the 10-day
  volume weighted average trading price of an OGS Share on 22 January 2003,
  the last UK Business Day prior to the announcement by CAT and OGS of their
  agreed merger

  an additional 33.5p per OGS Share, equivalent to a premium of
  approximately 22.6 per cent. over 148.5p, being the implied value of an
  OGS Share under the CAT merger offer, on 25 February 2003, the last UK
  Business Day prior to the announcement by Celltech of the Offer

4.Background to and reasons for the Offer

  Celltech believes that its cash offer represents an opportunity to acquire
  important tangible and intangible assets that it can harness into its
  extensive R&D capabilities.

  Celltech believes that, using its various antibody and small molecule
  technology platforms, it has the ability to exploit certain novel protein
  disease targets identified and patented by OGS. In addition, Celltech
  believes that the integration of OGS' bio-informatics capabilities will
  expand its own capabilities in this area. Zavesca, OGS' licensed product
  for the treatment of mild to moderate Type I Gaucher disease, will
  generate a future income stream that will be of value to Celltech.

  Further, Celltech believes that its cash offer represents a significant
  premium to the value of CAT's share offer, announced on 23 January 2003.
  The proposed transaction between CAT and OGS values each OGS share at
  148.5 pence as at the close of business on 25 February 2003. This equates
  to a valuation for OGS of GBP82.8 million against a value of OGS on 22
  January 2003 (the last UK Business Day before the announcement by CAT and
  OGS of their agreed merger) of GBP85.0 million.

  Celltech has previously indicated to its shareholders that, since its
  existing business is cash-generative, it does not need to raise funds for
  existing operations or small product or technology acquisitions. In
  keeping with this philosophy, and to avoid any dilution for its existing
  shareholders, Celltech is offering 182 pence in cash for each OGS Share
  (including those represented by OGS ADSs), equating to a valuation for OGS
  of GBP101.4 million.

5.Financial effects on Celltech

  Celltech plans to undertake a rapid integration of OGS, which is expected
  to be substantially complete in the second half of 2003. The financial
  impact on Celltech's earnings profile is anticipated to be negligible.

6.The Loan Note Alternative

  OGS Securityholders (other than certain overseas OGS Securityholders) who
  validly accept the Offer will be able to elect to receive Loan Notes
  instead of some or all of the cash to which they would otherwise become
  entitled under the terms of the Offer. The Loan Note Alternative will be
  available on the following basis:

  for every GBP1 in cash consideration GBP1 nominal of Loan Notes

  The Loan Notes, which will be governed by English law, will be unsecured
  and will be issued credited as fully paid in amounts and integral multiples
  of GBP1 nominal value. All fractional entitlements to the Loan Notes will be
  disregarded. No application will be made for the Loan Notes to be listed or
  dealt in or on any stock exchange but they shall be transferable subject to
  certain restrictions to be set out in the instrument constituting the Loan
  Notes.

  The Loan Notes will carry interest at 0.5 per cent. below LIBOR. Interest
  will be payable by half-yearly instalments in arrears (less any tax) on 30
  June and 31 December in each year, except that the first payment of interest
  will be made on the date (the "First Interest Payment Date") which is the
  first 30 June or 31 December to fall on or after the date which is six
  months after the first date of issue of any of the Loan Notes. On the
  First Interest Payment Date, interest will be paid in respect of the period
  from (and including) the first date of issue of any of the Loan Notes to
  (but excluding) the First Interest Payment Date. The Loan Notes will be
  redeemable in whole or in part for cash at the option of holders on th
  First Interest Payment Date and subsequent interest payment dates. In
  certain circumstances (to be set out in the instrument constituting
  the Loan Notes), Celltech will have the right to redeem all of the
  Loan Notes. The final redemption date will be the fifth anniversary of
  the First Interest Payment Date.

  No Loan Notes will be issued unless, on or before the date on which the
  Offer becomes or is declared unconditional in all respects, valid elections
  have been received in respect of at least GBP10 million in nominal value
  of Loan Notes. If insufficient elections are received, Celltech reserves
  the right to choose, for those OGS Securityholders electing for the Loan
  Note Alternative, whether to honour those elections received or to settle
  in cash in accordance with the terms of the Offer.

  Subject as aforesaid, the Loan Note Alternative will remain open for
  acceptance for as long as the Offer remains open for acceptance. The Loan
  Note Alternative is conditional upon the Offer becoming or being declared
  unconditional in all respects.

  Further details of the Loan Notes will be included in the Offer Document.
  OGS Securityholders who are not resident in the United Kingdom should refer
  to paragraph 13 below.

7.Information on the Celltech Group

  Celltech is a leading European biotechnology company, with an extensive late
  stage development pipeline and a profitable, cash-generative pharmaceutical
  business. Celltech also possesses significant drug discovery and development
  capabilities, including a world-leading antibody technology platform and
  extensive medicinal chemistry capabilities.

  Celltech is pursuing an R&D-centred strategy, where it aims to build long-
  term shareholder value by bringing first-in-class or best-in-class products
  to market, with its substantial investment in R&D of some GBP100 million per
  annum being sustained by revenues from its pharmaceutical business and
  royalty streams. Celltech is focused upon maximising the value retained from
  its innovative development programmes whilst minimising risk. This approach
  includes partnering for strength, where Celltech retains co-promotion rights,
  profit-sharing arrangements and enhanced royalties. These commercialisation
  arrangements include the marketing of certain specialist-focused products
  using Celltech's own salesforce. Celltech has product collaborations with
  leading pharmaceutical and biotechnology companies including Amgen,
  AstraZeneca, Biogen, Bristol-Myers Squibb, Johnson & Johnson, Merck,
  Pharmacia and Wyeth.

  For the year ended 31 December 2001, the Celltech Group reported a profit
  before taxation and goodwill amortisation of GBP47.8 million (loss of GBP
  56.2 million after goodwill amortisation) on turnover of GBP303.1 million.
  The Celltech Group had net assets as at that date of GBP619.2 million.
  As at close of business on 25 February 2003, Celltech had a market
  capitalisation of GBP892.1 million.

8.Information on OGS

  OGS is a research and product development company with three distinct
  business units - Inherited Storage Disorders (ISD), proteomics and oncology.
  In ISD, its most advanced product is Zavesca , which has been approved by
  the European Commission for the treatment of mild to moderate Type I Gaucher
  disease in patients for whom enzyme replacement therapy is unsuitable. Under
  the terms of a marketing and distribution agreement, Actelion will market
  Zavesca worldwide with the exception of Israel. European launch is expected
  in March 2003. An amended New Drug Application is expected to be filed with
  the FDA in the first quarter of 2003. In Israel Zavesca will be marketed by
  Teva, who filed for approval in January 2003. Zavesca is also undergoing
  further clinical investigations in other glycosphineal storage disorders.
  Another ISD compound is OGT 923, which has entered Phase I clinical trials.

  OGS has a leading proteomics business which has several collaborations with
  partners including Bayer, GSK, Pfizer, Pioneer Hi-Bred/DuPont and Wyeth. In
  addition it has a joint venture, Confirmant Limited, to develop the protein
  atlas of the human genome. OGS receives royalties for licensing its
  intellectual property in proteomics.

  In oncology, OGS is developing a pipeline of projects and has drug discovery
  and development alliances with Medarex and BioInvent and a drug discovery
  alliance with NeoGenesis. OGS currently has five discovery products in
  oncology.

  OGS completed its initial public offering and listing on the London Stock
  Exchange in April 1998, raising approximately GBP27.8 million. In March 2000,
  OGS raised approximately GBP32.9 million and in December raised a further
  GBP157.4 million in secondary offerings. In December 2000, the OGS ADSs
  commenced trading on NASDAQ.

  For the year ended 31 December 2001, OGS reported a loss before taxation of
  GBP28.2 million on turnover of approximately GBP13.4 million. OGS had net
  assets as at that date of approximately GBP194.6 million, with net cash of
  approximately GBP176.6 million. On the basis of the Closing Price of an OGS
  Share of 152.5 pence on 22 January 2003, the last UK Business Day prior to
  the date of the announced merger with CAT, OGS' market capitalisation was
  approximately GBP85.0 million. As at 31 December 2002, OGS had net cash of
  approximately GBP136.4 million.

9.Management and employees

  The Celltech Board confirms that the existing contractual employment rights,
  including pension rights, of the management and employees of the OGS Group
  will be fully safeguarded following completion of the Offer.

10.Financing
  The Offer will be funded from Celltech's existing cash resources and credit
  facilities. As of 31 December 2002, Celltech had cash and liquid resources
  of GBP105.1 million, offset by GBP31.2 million in loan notes, and has
  committed 3 year credit facilities of GBP65 million available from a
  syndicate of banks.  JPMorgan has confirmed that resources are available
  to Celltech sufficient to satisfy full acceptance of the Offer.

11.OGS Share Option Schemes

  The Offer extends to any shares in OGS which are unconditionally allotted
  or issued pursuant to the exercise of existing options under the OGS Share
  Option Schemes while the Offer remains open for acceptance (or such earlier
  date as Celltech may, subject to the City Code, decide).

  Appropriate proposals will be made to holders of options under the OGS Share
  Option Schemes as soon as practicable. Such proposals will be conditional
  upon the Offer becoming or being declared unconditional in all respects.

12.OGS/CAT Scheme

  OGS Securityholders should be aware that it is a condition of the Offer that
  the OGS/CAT Scheme does not become effective. Any OGS Shareholder who wishes
  to accept the Offer should make an election in the forms of proxy provided in
  relation to the OGS/CAT Scheme to vote against the resolutions to approve the
  OGS/CAT Scheme to be proposed at the OGS Court Meeting and the OGS EGM. Any
  OGS ADS Holder who wishes to accept the Offer should make an instruction in
  the voting instruction card provided in relation to the OGS/CAT Scheme to
  vote against the resolutions to be proposed at the OGS Court Meeting and the
  OGS EGM.

 13.Overseas Holders of OGS Securities

  The availability of the Offer to persons not resident in the UK or the US
  may be affected by the laws of the relevant jurisdiction. Persons who are
  not resident in the UK or the US should inform themselves about and observe
  any applicable requirements.

  The Offer in the United States is made solely by Celltech, and neither
  JPMorgan nor any of its affiliates is making the Offer in the United States.
  Unless otherwise determined by Celltech and permitted by applicable law and
  regulation, the Offer (including the Loan Note Alternative) is not being
  made, directly or indirectly, in or into, Australia, Canada or Japan and,
  subject to certain exemptions, the Offer is not capable of acceptance from
  or within Australia, Canada or Japan. Accordingly, neither this announcement,
  the Offer Document nor the Acceptance Forms are being or may be mailed or
  otherwise forwarded, distributed or sent into or from Australia, Canada or
  Japan and doing so may render any purported acceptance of the Offer invalid.
  All OGS Securityholders (including nominees, trustees or custodians) who
  may have a contractual or legal obligation, or may otherwise intend, to
  forward any or all of this announcement, the Offer Document and the
  Acceptance Forms, should read the further details in this regard which will
  be contained in the Offer Document before taking any action.

  The Loan Notes to be issued pursuant to the Loan Note Alternative have not
  been, and will not be, listed on any stock exchange and have not been and
  will not be registered under the US Securities Act or under any relevant
  securities laws of any state or other jurisdiction of the United States, or
  under the relevant securities laws of Australia, Canada or Japan or any
  other jurisdiction. Accordingly, unless an exemption under such relevant
  laws is available, Loan Notes may not be offered, sold, re-sold or delivered,
  directly or indirectly, in, into or from the United States, Australia,
  Canada or Japan or any other jurisdiction in which an offer of Loan Notes
  would constitute a violation of relevant laws or require registration
  thereof, or to or for the account or benefit of any US Person or resident
  in Australia, Canada or Japan or any other such jurisdiction.

  Notwithstanding the foregoing, Celltech retains the right to permit the
  Offer to be accepted and any sale of OGS Securities pursuant to the Offer
  to be completed if, in its sole discretion, it is satisfied that the
  transaction in question can be undertaken in compliance with applicable
  law and regulation.

14.Rights of Withdrawal

  Except to the extent of the exemptive relief which may be granted by the
  SEC, the Offer is subject to the US tender offer rules applicable to
  securities registered under the Exchange Act, as well as to the City Code.
  This has necessitated a number of changes from the procedures which
  normally apply to offers for companies governed by the City Code,
  including those applicable to the rights of OGS Securityholders to
  withdraw their acceptance of the Offer. Under the Offer, OGS
  Securityholders will be able to withdraw their acceptances at any time
  during the Initial Offer Period but will not have any withdrawal rights
  during the Subsequent Offer Period, except in certain limited
  circumstances. The Subsequent Offer Period must remain open for at least
  14 days but may be extended.

  The Offer will be deemed not to have been validly accepted in respect of
  any OGS Shares (including those represented by OGS ADSs), acceptances in
  respect of which have been validly withdrawn. However, the Offer may be
  accepted again in respect of any withdrawn OGS Securities by following
  one of the procedures which will be described in the Offer Document at
  any time prior to expiry or lapse of the Offer.

  It should be noted that by virtue of the conflicting provisions of the
  City Code and US federal securities laws, the Panel has agreed that the
  Acceptance Condition can be structured so that the Offer cannot become
  or be declared unconditional as to acceptances until such time as all
  other Conditions to the Offer have been satisfied, fulfilled or, to the
  extent permitted, waived. The Acceptance Condition in paragraph (a) of
  Part A of Appendix I to this announcement reflects this. Further details
  of these rights of withdrawal and the procedure for effecting withdrawals
  will be set out in the Offer Document.

15.Compulsory acquisition and application for de-listing

  If Celltech receives acceptances under the Offer in respect of, and/or
  otherwise acquires, 90 per cent or more of the OGS Shares (including those
  represented by OGS ADSs) to which the Offer relates, Celltech intends to
  exercise its rights pursuant to the provisions of sections 428 to 430F of
  the Companies Act to acquire compulsorily the remaining OGS Shares
  (including those represented by OGS ADSs).

  Furthermore, as soon as it is appropriate and possible to do so and subject
  to the Offer becoming or being declared unconditional in all respects,
  Celltech intends to procure the making of an application by OGS to the
  London Stock Exchange and the UK Listing Authority respectively for the
  cancellation of the trading in OGS Shares on the London Stock Exchange's
  market for listed securities and the listing of the OGS Shares on the
  Official List and intends to seek to re-register OGS as a private company
  under the relevant provisions of the Companies Act. It is anticipated that
  such cancellation will take effect not earlier than 20 UK Business Days
  after the offer becomes or is declared unconditional in all respects. De-
  listing would significantly reduce the liquidity and marketability of any
  OGS Shares not assented to the Offer.  Celltech also intends that OGS applies
  for the de-listing of OGS ADSs from NASDAQ which would significantly reduce
  the liquidity and marketability of any OGS ADSs. Celltech may also request
  that OGS terminates the existing deposit agreement through which the OGS ADS
  programme is operated.

16.General

  To the best of Celltech's knowledge and belief, and save as disclosed in
  this announcement, neither Celltech nor any director of Celltech, nor any
  person acting in concert with Celltech, owns or controls any OGS Securities
  or any securities convertible or exchangeable into, or any rights to
  subscribe for or purchase, or any options to purchase any OGS Securities or
  holds any derivatives referenced to OGS Securities.

  The Offer will be made by Celltech and (outside the United States) by
  JPMorgan on its behalf.

  This announcement does not constitute an offer or invitation to purchase
  any securities or a solicitation of an offer to buy any securities, pursuant
  to the Offer or otherwise.

  The conditions and certain further terms of the Offer are set out in Appendix
  I.

  Details of the sources of information and bases of calculation used in this
  announcement are set out in Appendix II.

  Definitions used in this announcement are set out in Appendix III.

17.Offer documentation

  The formal Offer Document will be sent to OGS Securityholders shortly and,
  for information only, to participants in the OGS Share Option Schemes. The
  Offer will be on terms and will be subject to the conditions which are set
  out in Appendix I and to those terms which will be set out in the Offer
  Document and in the accompanying Acceptance Forms, and such further terms
  as may be required to comply with the rules and regulations of the Financial
  Services Authority, the UK Listing Authority and the London Stock Exchange
  and with the City Code and US federal securities laws (except to the extent
  of any exemptive relief granted by the SEC).

There will be a presentation to analysts at 09:30 a.m. today in the Great Hall
at JPMorgan, 60 Victoria Embankment, London, EC4Y 0JP. A live webcast of this
presentation will be available on www.celltechgroup.com, with a replay facility
available for approximately 30 business days thereafter.

Enquiries:
For further information contact:

Celltech Group plc Telephone: +44 (0)1753 534 655

Dr Peter Fellner, Chief Executive

Peter Allen, Chief Financial Officer

Richard Bungay, Director of Corporate Communications

JPMorgan Telephone: +44 (0)20 7742 4000

Bernard Taylor, Vice Chairman

Julian Oakley, Managing Director

Brunswick London

Jon Coles Telephone: +44 (0)20 7404 5959

Fiona Fong

Brunswick New York

Cindy Leggett-Flynn Telephone: +1 212 333 3810

This announcement does not constitute an offer or invitation to purchase any
securities or a solicitation of an offer to buy any securities, pursuant to the
Offer or otherwise. The Offer will be made solely by the Offer Document and the
Acceptance Forms accompanying the Offer Document, which will contain the full
terms and conditions of the Offer, including details of how the Offer may be
accepted. Celltech will be filing a Tender Offer Statement containing the Offer
Document and other related information on the date the Offer Document is mailed
to OGS Securityholders. Free copies of those documents will be available on the
SEC's website at

www.sec.gov.

The Offer Document and the Acceptance Forms
accompanying the Offer Document will be made available to all OGS
Securityholders at no charge to them. OGS Securityholders are advised to read
the Offer Document and the accompanying Acceptance Forms when they are sent to
them because they will contain important information. OGS Securityholders in
the US are also advised to read the Tender Offer Statement because it will
contain important information.

Unless otherwise determined by Celltech and permitted by applicable law and
regulation, the Offer (including the Loan Note Alternative) will not be made,
directly or indirectly, in or into, or by use of the mails of, or by any other
means or instrumentality (including, without limitation, telephonically or
electronically) of interstate or foreign commerce of, or of any facility of a
national securities exchange of Canada, nor will it be made in or into
Australia or Japan and the Offer will not be capable of acceptance by any such
use, means, instrumentality or facilities or from within Australia, Canada or
Japan.

Accordingly, unless otherwise determined by Celltech and permitted by
applicable law and regulation, neither copies of this announcement nor any
other documents relating to the Offer are being, or may be, mailed or
otherwise forwarded, distributed or sent in or into Australia, Canada or
Japan and persons receiving such documents (including custodians, nominees
and trustees) must not distribute or send them in, into or from such
jurisdictions.
The Loan Notes to be issued pursuant to the Loan Note Alternative have not
been, and will not be, listed on any stock exchange and have not been and
will not be registered under the US Securities Act or under any relevant
securities laws of any state or other jurisdiction of the United States, or
under the relevant securities laws of Australia, Canada or Japan or any other
jurisdiction. Accordingly, unless an exemption under such relevant laws is
available, Loan Notes may not be offered, sold, re-sold or delivered, directly
or indirectly, in, into or from the United States, Australia, Canada or Japan
or any other jurisdiction in which an offer of Loan Notes would constitute a
violation of relevant laws or require registration of the Loan Notes, or to
or for the account or benefit of any US Person or resident of Australia,
Canada or Japan or any other such jurisdiction.

JPMorgan is acting for Celltech and for no one else in connection with the
Offer and will not be responsible to anyone other than Celltech for providing
the protections afforded to customers of JPMorgan or for providing advice in
relation to the Offer.

The Panel wishes to draw the attention of member firms of NASDAQ to certain UK
dealing disclosure requirements during the offer period. The offer period (in
accordance with the City Code, which is published and administered by the
Panel) commences at the time when an announcement is made of a proposed or
possible offer, with or without terms. OGS has equity securities traded on the
London Stock Exchange and NASDAQ.

The above disclosure requirements are set out in more detail in Rule 8 of the
City Code. In particular, Rule 8 requires public disclosure of dealings during
the offer period by persons who own or control, or who would as a result of any
transaction own or control, one per cent. or more of any class of relevant
securities of the offeree company. Relevant securities include OGS Shares, OGS
ADSs and instruments convertible into OGS Shares or OGS ADSs. This requirement
will apply until the first closing date or, if this is later, the date when the
Offer becomes or is declared unconditional or lapses.

Disclosure should be made on an appropriate form by no later than 12 noon
London time (7 a.m. New York City time) on the business day following the date
of the dealing transaction. These disclosures should be published through a
Regulatory Information Service.

The Panel requests that member firms advise those of their clients who wish to
deal in the relevant securities of OGS, whether in the United States or in the
UK, that they may be affected by these requirements. If there is any doubt as
to their application the Panel should be consulted (telephone number: +44 (0)
20 7382 9026, fax number: +44 (0) 20 7638 1554).

This announcement contains certain "forward-looking" statements which are
naturally subject to uncertainty and changes in circumstances. Actual results
may vary materially from the expectations contained in this announcement. The
forward-looking statements contained in this announcement include statements
about the feasibility and benefits of the acquisition of OGS by Celltech.
Factors that would cause actual results to differ materially from those
described in this announcement include: the inability to obtain necessary
regulatory approvals or to obtain them on acceptable terms; the inability
successfully to integrate OGS within the Celltech Group or to realise
synergies from such integration; costs related to the acquisition of OGS;
the economic environment of the industries in which Celltech and OGS operate;
the general economic environment; and other risk factors detailed in OGS' and
Celltech's filings with the SEC.

This announcement has been approved by JPMorgan for the purpose of section 21
of the Financial Services and Markets Act 2000 only.


APPENDIX I

CONDITIONS AND CERTAIN FURTHER TERMS OF THE OFFER

The Offer, which will be made by Celltech and (outside the United States) by
JPMorgan on its behalf, complies with the applicable rules and regulations of
the City Code and with the Exchange Act. In addition, the Offer will be
governed by English law and will be subject to the jurisdiction of the courts
of England and will be made on the terms and conditions set out below and in
the Acceptance Forms.

Part A: Conditions of the Offer

The Offer will be subject to the following conditions:

(a) valid acceptances being received (and not, where permitted, withdrawn) by
3.00 p.m. (London time), 10.00 a.m. (New York City time) on the day following
the twentieth US Business Day following the date of the Offer or such later
time(s) and/or date(s) as Celltech may, subject to the City Code, decide in
respect of not less than 90 per cent. in nominal value (or such lesser
percentage as Celltech may decide) of the OGS Shares (including OGS Shares
represented by OGS ADSs) to which the Offer relates, provided that this
condition will not be satisfied unless Celltech and its wholly-owned
subsidiaries shall have acquired, or agreed to acquire, pursuant to the Offer
or otherwise, OGS Shares (including OGS Shares represented by OGS ADSs)
carrying more than 50 per cent. of the voting rights normally exercisable
at a general meeting of OGS, including for this purpose (to the extent, if
any, required by the Panel) any such voting rights attaching to any OGS Shares
(including OGS Shares represented by OGS ADSs) that are unconditionally
allotted or issued before the Offer becomes or is declared unconditional as
to acceptances whether pursuant to the exercise of any outstanding subscription
or conversion rights or otherwise and for the purposes of this condition:

(i) OGS Shares (including OGS Shares represented by OGS ADSs) which have been
unconditionally allotted but not issued shall be deemed to carry the voting
rights they will carry on issue; and

(ii) the expression "OGS Shares (including OGS Shares represented by OGS ADSs)
to which the Offer relates" shall be construed in accordance with sections 428
to 430F of the Companies Act 1985,

provided further that, unless Celltech otherwise determines, this condition (a)
shall be capable of being satisfied only at a time when all of the other
conditions (b) to (j) inclusive have been either satisfied, fulfilled or, to
the extent permitted, waived;

(b) the Office of Fair Trading indicating, in terms reasonably satisfactory to
Celltech, that it is not the intention of the Secretary of State for Trade and
Industry to refer the proposed acquisition of OGS by Celltech, or any matter
arising therefrom, to the Competition Commission;

(c) insofar as the Offer, or any matter arising therefrom, constitutes a
concentration that must be notified in accordance with Section 39 of the German
Act against Restraints of Competition ("ARC", Gesetz gegen
Wettbewerbsbeschrankungen), (i) notification from the German Federal Cartel
Office ("FCO") that the conditions for a prohibition of the proposed
acquisition of shares in, or control of, OGS by Celltech set out in Section
36 para.1 of the ARC are not fulfilled; or (ii) the expiry of the one month
time limit laid down in Section 40 para.1 of the ARC without Celltech having
been notified by the FCO that it has entered into an examination of the
proposed acquisition of shares in, or control of, OGS by Celltech; or (iii)
approval or deemed approval of the proposed acquisition of shares in, or
control of, OGS by Celltech by the FCO pursuant to Section 40 para.2 of the
ARC;
(d) the OGS/CAT Scheme (or any other scheme of arrangement under section 425
of the Companies Act between OGS and the OGS Shareholders which may be proposed
to effect a merger between CAT and OGS) shall not have become effective in
accordance with its terms;

(e) no government or governmental, quasi-governmental, supranational, statutory
or regulatory body or association, institution or agency (including any trade
agency) or any court or other body (including any professional or environmental
body) or person in any jurisdiction (each a "Relevant Authority") having
decided to take, instituted or threatened any action, proceeding, suit,
investigation, enquiry or reference or enacted, made or proposed and there not
continuing to be outstanding any statute, regulation, order or decision that
would or might be reasonably expected to:

(i) make the Offer or the acquisition or the proposed acquisition of any shares
in, or control of, OGS by Celltech void, unenforceable or illegal or directly
or indirectly prohibit or otherwise materially restrict, delay or interfere
with the implementation of, or impose material additional conditions or
obligations with respect to, or otherwise challenge, the Offer or the
acquisition of any shares in, or control of, OGS by Celltech;

(ii) require, prevent or delay the divestiture (or alter the terms of any
proposed divestiture) by the Wider Celltech Group or the Wider OGS Group of all
or any substantial part of their respective businesses, assets or properties or
impose any limitation on their ability to conduct all or any part of their
respective businesses and to own any of their respective assets or properties;

(iii) impose any material limitation on, or result in any material delay in,
the ability of any member of the Wider Celltech Group to acquire or hold or to
exercise effectively, directly or indirectly, all or any rights of ownership of
shares or other securities (or the equivalent) in, or to exercise management
control over, any member of the Wider OGS Group or on the ability of any member
of the Wider OGS Group to hold or exercise effectively, directly or indirectly,
all or any rights of ownership of shares or other securities (or the
equivalent) in, or to exercise management control over, any other member of
the Wider OGS Group in each case to an extent which is material in the context
of the Wider Celltech Group taken as a whole or, as the case may be, the Wider
OGS Group taken as a whole;

(iv) require any member of the Wider Celltech Group or of the Wider OGS Group
to acquire or offer to acquire any shares or other securities (or the
equivalent) in any member of the Wider OGS Group or any member of the Wider
Celltech Group where such acquisition would be material in the context of
the Wider Celltech Group taken as a whole in the context of the Offer or, as
the case may be, the Wider OGS Group taken as a whole;

(v) impose any material limitation on the ability of any member of the Wider
Celltech Group or the Wider OGS Group to integrate or co-ordinate its business,
or any part of it, with the businesses or any part of the businesses of any
other member of the Wider Celltech Group and/or the Wider OGS Group; or

(vi) otherwise materially and adversely affect the business, assets, financial
or trading position or profits of any member of the Wider Celltech Group or of
the Wider OGS Group,

and all applicable waiting and other time periods during which any such
Relevant Authority could decide to take, institute or threaten any such
action, proceeding, suit, investigation, enquiry or reference having expired,
lapsed or been terminated;

(f) all necessary filings having been made and all appropriate waiting periods
(including any extensions thereof) under any applicable legislation or
regulation of any jurisdiction having expired, lapsed or been terminated in
each case in respect of the Offer and the acquisition of any shares in, or
control of, OGS by Celltech and all authorisations, orders, grants,
recognitions, confirmations, licences, consents, clearances, permissions
and approvals ("authorisations") necessary or appropriate in any jurisdiction
for or in respect of the Offer and the proposed acquisition of any shares in,
or control of, OGS by Celltech being obtained in terms and in a form reasonably
satisfactory to Celltech from appropriate Relevant Authorities or from any
persons or bodies with whom any member of the Wider Celltech Group or the Wider
OGS Group has entered into contractual arrangements and such authorisations
together with all authorisations necessary or appropriate for any member of the
Wider OGS Group to carry on its business remaining in full force and effect and
no intimation of any intention to revoke, suspend, restrict or modify or not to
renew any of the same having been made and all necessary statutory or
regulatory obligations in any jurisdiction having been complied with;

(g) save as fully and fairly disclosed to Celltech in writing before the date
of this announcement, there being no provision of any agreement, arrangement,
licence or other instrument to which any member of the Wider OGS Group is a
party or by or to which any such member or any of its assets is or may be
bound, entitled or subject which, as a result of the making or implementation
of the Offer or the acquisition or proposed acquisition by Celltech of any
shares in, or change in the control or management of, OGS or otherwise, would
or might (to an extent which is materially adverse in the context of the Wider
OGS Group taken as a whole) reasonably be expected to result in:

(i) any monies borrowed by or any other indebtedness (actual or contingent) of
any such member of the Wider OGS Group becoming repayable or capable of being
declared repayable immediately or earlier than the stated repayment date or
the ability of such member to borrow monies or incur any indebtedness being
withdrawn or inhibited;

(ii) the creation or enforcement of any mortgage, charge or other security
interest over the whole or any part of the business, property or assets of
any such member of the Wider OGS Group or any such security interest (whenever
arising or having arisen) becoming enforceable;

(iii)any assets or interest of any such member of the Wider OGS Group being or
falling to be disposed of or charged or any right arising under which any such
asset or interest could be required to be disposed of or charged, other than
in the ordinary course of business;

(iv)the interest or business of any such member of the Wider OGS Group in or
with any other person, firm or company (or any agreements or arrangements
relating to such interest or business) being terminated or adversely affected;

(v) any such member of the Wider OGS Group ceasing to be able to carry on
business under any name under which it presently does so;

(vi)the value of any such member of the Wider OGS Group or its financial or
trading position being prejudiced or adversely affected;

(vii)any such agreement, arrangement, licence or other instrument being
terminated or adversely modified or any onerous obligation arising or any
adverse action being taken or arising thereunder; or

(viii)the creation of any liabilities (actual or contingent) by any such
member of the Wider OGS Group;

and no event having occurred which, under any provision of any agreement,
arrangement, licence or other instrument to which any member of the Wider OGS
Group is a party or by or to which any such member or any of its assets may be
bound or be subject, could result in any events or circumstances as are
referred to in sub-paragraphs (i) to (viii) of this paragraph (g);

(h) except as disclosed in the annual report and accounts of OGS for the year
ended 31 December, 2001, or the interim financial statements of OGS for the six
months ended 30 June, 2002 or as publicly announced to a Regulatory Information
Service by or on behalf of OGS or as otherwise fairly disclosed to Celltech in
writing before the date of this announcement, no member of the Wider OGS Group
having since 31 December, 2001:

(i) issued or agreed to issue or authorised the issue of additional shares of
any class, or securities convertible into, or rights, warrants or options to
subscribe for or acquire, any such shares or convertible securities save as
between OGS and wholly-owned subsidiaries of OGS prior to the date of this
announcement, or upon the exercise of rights to subscribe for OGS Shares
pursuant to options granted under the OGS Share Option Schemes prior to the
date of this announcement;

(ii) recommended, declared, paid or made any bonus, dividend or other
distribution, whether payable in cash or otherwise, other than a distribution
by any wholly-owned subsidiary of OGS;

(iii) implemented or authorised any merger or demerger or (other than in the
ordinary course of business) acquired or disposed of or transferred, mortgaged
or charged, or created any other security interest over, any asset or any
right, title or interest in any asset;

(iv) implemented or authorised any reconstruction, amalgamation, scheme or
other transaction or arrangement (other than in the ordinary course of
business);
(v) purchased, redeemed or repaid any of its own shares or other securities
or reduced or made or authorised any other change in its share capital;

(vi) made or authorised any change in its loan capital or issued or
authorised the issue of any debentures or (other than in the ordinary course
of business and save as between OGS and wholly-owned subsidiaries of OGS)
incurred or increased any indebtedness or contingent liability;

(vii) entered into, varied or terminated, or authorised the entry into,
variation or termination of, any contract, commitment or arrangement (whether
in respect of capital expenditure or otherwise) which is outside the ordinary
course of business or which is of a long term, onerous or unusual nature or
magnitude or which involves or could involve an obligation of a nature or
magnitude which is material;

(viii)entered into any contract, commitment or arrangement which would be
restrictive on the business of any member of the Wider OGS Group or the Wider
Celltech Group (other than to a nature and extent which is not material in
the context of the business concerned);

(ix) been unable, or admitted in writing that it is unable, to pay its debts
or having stopped or suspended (or threatened to stop or suspend) payment of
its debts generally or ceased or threatened to cease carrying on all or a
substantial part of its business;

(x) taken any corporate action or had any legal proceedings started or
threatened against it for its winding-up (voluntary or otherwise), dissolution
or reorganisation (or for any analogous proceedings or steps in any
jurisdiction) or for the appointment of a receiver, administrator,
administrative receiver, trustee or similar officer (or for the appointment of
any analogous person in any jurisdiction) of all or any of its assets and
revenues;

(xi) waived, compromised or settled any claim which is material in the context
of the Wider OGS Group taken as a whole;

(xii) entered into or varied the terms of any service agreement or arrangement
with any director of OGS;

(xiii)made or consented to any significant change to the terms of the trust
deeds constituting the pension schemes established for its directors and/or
employees and/or their dependants or to the benefits which accrue, or to the
pensions which are payable thereunder, or to the basis on which qualification
for or accrual or entitlement to such benefits or pensions are calculated or
determined, or to the basis upon which the liabilities (including pensions) of
such pension schemes are funded or made, or agreed or consented to, any change
to the trustees, in each case which is material; or

(xiv)entered into any contract, commitment or arrangement or passed any
resolution or made any offer (which remains open for acceptance) with respect
to, or proposed or announced any intention to effect or propose, any of the
transactions, matters or events referred to in this condition;

and for the purpose of this condition "material" shall mean material in the
context of the OGS Group taken as a whole;

(i) since 31 December, 2001 (except as disclosed in the annual report and
accounts of OGS for the year then ended or the interim financial statements of
OGS for the six months ended 30 June, 2002 or as publicly announced to a
Regulatory Information Service by or on behalf of OGS before the date of this
announcement);

  (i) no adverse change having occurred in the business, assets, financial or
  trading position or profits of the Wider OGS Group which is material in the
  context of the OGS Group taken as a whole;

  (ii) no litigation, arbitration proceedings, prosecution or other legal
  proceedings having been threatened, announced, instituted or remaining
  outstanding by, against or in respect of any member of the Wider OGS Group
  or to which any member of the Wider OGS Group is a party (whether as
  plaintiff or defendant or otherwise) and no investigation by any Relevant
  Authority or other investigative body against or in respect of any member
  of the Wider OGS Group having been threatened, announced, instituted or
  remaining outstanding by, against or in respect of any member of the Wider
  OGS Group which would or might materially and adversely affect the Wider
  OGS Group taken as a whole; and

  (iii) no contingent or other liability having arisen which would or might
  materially and adversely affect the Wider OGS Group taken as a whole;

(j) Celltech not having discovered that:

(i) any financial, business or other information publicly disclosed at any time
by any member of the Wider OGS Group is misleading, contains a
misrepresentation of fact or omits to state a fact necessary to make the
information contained therein not misleading which in any case is material to
the financial or trading position of the Wider OGS Group taken as a whole;

(ii) any member of the Wider OGS Group is subject to any liability, contingent
or otherwise, which is not disclosed in the annual report and accounts of OGS
for the year ended 31 December, 2001 or the interim financial statements of OGS
for the six months ended 30 June, 2002 and which is material in the context of
the Wider OGS Group taken as a whole;

(iii)any past or present member of the Wider OGS Group has failed to comply
with any applicable legislation or regulations of any jurisdiction or any
notice or requirement of any Relevant Authority with regard to the storage,
disposal, discharge, spillage, release, leak or emission of any waste or
hazardous or harmful substance or any substance likely to impair the
environment or harm human or animal health or otherwise relating to
environmental matters or that there has otherwise been any such storage,
disposal, discharge, spillage, release, leak or emission (whether or not
the same constituted non-compliance by any person with any such legislation
or regulation, and whenever the same may have taken place), any of which non-
compliance would be likely to give rise to any liability (whether actual or
contingent) or cost on the part of any member of the Wider OGS Group and which
is material in the context of the Wider OGS Group taken as a whole; or

(iv)there is or is likely to be any obligation or liability (whether actual or
contingent) to make good, repair, re-instate or clean up any property now or
previously owned, occupied, operated or made use of or controlled by any past
or present member of the Wider OGS Group under any environmental legislation,
regulation, notice, circular or order of any Relevant Authority in any
jurisdiction and which is material in the context of the Wider OGS Group taken
as a whole.

Celltech reserves the right to waive all or any of conditions (b) to (j)
inclusive, in whole or in part. The Offer will lapse unless all the above
conditions are fulfilled or (if capable of waiver) waived or, where
appropriate, determined by Celltech to have been or remain satisfied by 3.00
p.m. (London time), 10.00 a.m. (New York City time) on the day following the
twentieth US Business Day following the date of the Offer (or such later date
as Celltech may determine, in accordance with the City Code and the Exchange
Act). Celltech shall be under no obligation to waive or treat as fulfilled any
of conditions (b) to (j) inclusive by a date earlier than the latest date for
the fulfilment thereof notwithstanding that the other conditions of the Offer
may at such earlier date have been waived or fulfilled and that there are at
such earlier date no circumstances indicating that any of such conditions may
not be capable of fulfilment.

If Celltech is required by the Panel to make an offer or offers for any OGS
Shares under Rule 9 of the City Code, Celltech may make such alterations to the
above conditions as are necessary to comply with that Rule.

The Offer will lapse (unless the Panel otherwise consents) if, before 3.00 p.m.
(London time), 10.00 a.m. (New York City time) on the day following the
twentieth US Business Day following the date of the Offer or the date when the
Offer becomes unconditional as to acceptances (whichever is the later), the
acquisition of OGS is referred to the Competition Commission.

Part B: Certain further terms of the Offer

The OGS Shares (including OGS Shares represented by OGS ADSs) will be acquired
by Celltech fully paid and free from all liens, equities, charges,
encumbrances, rights of pre-emption and other third party rights or interests
of any nature whatsoever and together with all rights, now or hereafter,
attaching thereto, including the right to receive and retain in full all
dividends and other distributions declared, made or paid on or after the
date of this announcement.

The availability of the Offer to persons not resident in the United Kingdom
may be affected by the laws of the relevant jurisdictions in which they are
located. Persons who are not resident in the United Kingdom should inform
themselves about, and observe, any applicable requirements.

The Offer will not be made, directly or indirectly, in or into Australia,
Canada or Japan. Accordingly, copies of this announcement are not being, and
must not be, mailed or otherwise distributed or sent in or into or from
Australia, Canada or Japan and doing so may render invalid any purported
acceptance of the Offer.

APPENDIX II

SOURCES OF INFORMATION AND BASES OF CALCULATION

General

Unless otherwise stated, financial information relating to Celltech has been
extracted from the relevant published audited annual report and accounts of
Celltech and/or the published interim results of Celltech and/or other public
statements made by Celltech. Unless otherwise stated, information relating to
OGS (including financial information) and the OGS/CAT Scheme has been extracted
from the relevant published audited annual report and consolidated financial
statements and/or from the published interim results of OGS, the documents
published by OGS and by CAT in connection with the OGS/CAT Scheme and/or other
public statements made by OGS.

Value of Offer

The level at which the Offer values the issued share capital of OGS is based
upon 55,729,534 OGS Shares in issue on 22 January 2003, the last UK Business
Day prior to the announcement by CAT and OGS of their agreed merger, and
excludes all OGS shares which could be issued upon exercise of any options
granted.
Market value of Celltech

The market value of Celltech is based on a Closing Price of 323.75p on 25
February 2003 and 275,552,386 million Celltech shares in issue, and excludes
all Celltech shares which could be issued upon exercise of any options granted.

Cash and liquid resources and loan notes of Celltech

The amount of cash and liquid resources at GBP105.1 million and loan notes at
GBP31.2 million as at 31 December 2002 have been taken from internal management
information of Celltech.

APPENDIX III

DEFINITIONS

      "Acceptance Condition" The condition in paragraph (a) of Part A of
       Appendix I

      "Acceptance Forms" The Form of Acceptance, and in relation to OGS ADS
       Holders only, the Letter of Transmittal and the Notice of Guaranteed
       Delivery

      "CAT" Cambridge Antibody Technology Group plc

      "Celltech" Celltech Group plc

      "Celltech Group" Celltech and its subsidiary undertakings

      "City Code" The City Code on Takeovers and Mergers

      "Closing Price" The closing middle-market quotation on the London Stock
       Exchange

      "Companies Act" The UK Companies Act 1985, as amended

      "Conditions" The conditions of the Offer set out in Appendix I to this
       announcement, and "Condition" means any one of them

      "Exchange Act" The US Securities Exchange Act of 1934 (as amended) and
       the rules and regulations promulgated thereunder

      "Form of Acceptance"The form of acceptance and authority and election
       relating to the Offer which will accompany the Offer Document for use
       by OGS Shareholders wishing to accept the Offer

      "Initial Offer Period"The period during which the Offer remains
       unconditional, which commences on the date of the Offer Document and
       expires on the earlier of the Offer lapsing or becoming or being
       declared unconditional in all respects in accordance with its terms

      "JPMorgan"J.P. Morgan plc

      "Letter of Transmittal" The letter of transmittal relating to the Offer
       which will accompany the Offer Document for use by OGS ADS Holders
       wishing to accept the Offer

      "LIBOR" The average (rounded down where necessary to the nearest whole
       multiple of one sixteenth of one per cent.) of the respective rates per
       annum at which any two London clearing banks selected by Celltech are
       prepared to offer six month sterling deposits of GBP1,000,000 to
       leading banks in the London inter bank market for sterling at or about
       11.00 a.m. (London time) on the first day of the relevant interest
       period or, if such a day is not a UK Business Day, on the next
       succeeding UK Business Day

      "Loan Note Alternative"The alternative under which certain OGS
       Securityholders who validly accept the Offer will be entitled to elect
       to receive Loan Notes instead of all or part of the cash consideration
       to which they would otherwise be entitled under the Offer

      "Loan Notes" The loan notes of Celltech to be issued pursuant to the
       Loan Note Alternative

      "London Stock Exchange" The London Stock Exchange plc

      "NASDAQ" The NASDAQ Stock Market Inc.

      "Notice of Guaranteed Delivery" The notice of guaranteed delivery
       relating to the Offer which will accompany the Offer Document for use
       by OGS ADS Holders

      "Offer" The offer to be made by Celltech and (outside the US) JPMorgan
       on its behalf to acquire all of the issued and to be issued OGS Shares
       (including those represented by OGS ADSs) on the terms and subject to
       the conditions to be set out in the Offer Document and the Acceptance
       Forms including, where the context so requires, any subsequent
       revision, variation, extension or renewal of such offer

      "Offer Document" The document containing the terms and conditions of
       the Offer, including the Loan Note Alternative, to be sent to OGS
       Securityholders

      "Official List" The Official List of the UK Listing Authority

      "OGS" Oxford GlycoSciences Plc

      "OGS ADSs" American Depositary Shares issued in respect of OGS Shares,
       each representing one OGS Share

      "OGS ADS Holders" Holders of OGS ADSs

      "OGS/CAT Scheme" The proposed scheme of arrangement under section 425
       of the Companies Act between OGS and the OGS Shareholders to give
       effect to the proposed merger of OGS and CAT, with, or subject to,
       any modification, addition or condition approved or imposed by the
       Court

      "OGS Court Meeting" The meeting of OGS Shareholders convened by order
       of the Court pursuant to section 425 of the Companies Act to consider,
       and if thought fit, approve the OGS/CAT Scheme, to be held on 11 March
       2003, including any adjournment thereof

      "OGS EGM" The extraordinary general meeting of OGS to consider any
       resolutions to approve and implement the OGS/CAT Scheme and the
       proposed merger of OGS and CAT, to be held on 11 March 2003, including
       any adjournment thereof

      "OGS Group" OGS and its subsidiary undertakings

      "OGS Securities" OGS Shares and OGS ADSs

      "OGS Securityholders" Holders of OGS Securities

      "OGS Shareholders" Holders of OGS Shares

      "OGS Shares" The existing unconditionally allotted or issued and fully
       paid ordinary shares of 5p each in OGS (including those represented by
       OGS ADSs) and any further such shares which are unconditionally allotted
       or issued while the Offer remains open for acceptance (or such earlier
       date, not being earlier than the date on which the Offer becomes or is
       declared wholly unconditional, as Celltech may, subject to the City
       Code, decide)

      "OGS Share Option Schemes" The OGS Limited 1989 Share Option Scheme, the
       OGS Group Plc 1994 Share Option Scheme, the OGS Executive Share Option
       Scheme and the OGS Sharesave Scheme

      "Panel" The Panel on Takeovers and Mergers

      "Regulatory Information Service" Any of the services set out in Schedule
       12 to the listing rules of the UK Listing Authority

      "R&D" Research and development

      "SEC" The United States Securities and Exchange Commission

      "Subsequent Offer Period" The period commencing immediately after the end
       of the Initial Offer Period during which the Offer will remain open for
       acceptance

      "Tender Offer Statement" The Tender Offer Statement on Schedule TO to be
       filed by Celltech with the SEC pursuant to Section 14(d) (1) of the
       Exchange Act

      "UK Business Day" A day other than a Saturday or a Sunday on which banks
       are generally open in London for normal business

      "UK Listing Authority"The Financial Services Authority acting in its
       capacity as the competent authority for the purposes of Part VI of the
       Financial Services and Markets Act 2000

      "United Kingdom" or "UK" The United Kingdom of Great Britain and Northern
       Ireland

      "US" or "United States" The United States of America, its territories and
       possessions, any State of the United States and the District of Columbia
      and all other areas subject to its jurisdiction

      "US Business Day"Any day, other than a Saturday, Sunday or a federal
       holiday in the United States, and consisting of the time period from
       12.01a.m. to 12.00 midnight Eastern (US) time

      "US Person" A US person as defined in Regulation S under the US
       Securities Act

      "US Securities Act" The US Securities Act of 1933, as amended

      "Wider Celltech Group"Celltech and its subsidiary undertakings,
       associated undertakings and any other undertakings in which Celltech
       and such undertakings (aggregating their interests) have a substantial
       interest

      "Wider OGS Group"OGS and its subsidiary undertakings, associated
       undertakings and any other undertakings in which OGS and such
       undertakings (aggregating their interests) have a substantial
       interest

      "GBP", "p", and "pence" Denote the lawful currency of the UK


END