Offer Update

For immediate release

Microgen plc

22 September 2004

Not for release, publication or distribution in whole or in part in or into the
United States, Canada, Australia or Japan

                               Recommended Offer                               

                            by UBS Investment Bank                             

                                 on behalf of                                  

                                 Microgen plc                                  

                              for AFA Systems plc                              

                   Posting of compulsory acquisition notices                   

On 13 September 2004, Microgen plc ('Microgen') released an announcement
declaring that the recommended offer made by UBS Investment Bank on behalf of
Microgen ('Offer') for AFA Systems plc ('AFA') was unconditional in all
respects.

The Board of Microgen announces that as at 3.00 pm on 21 September 2004, valid
acceptances of the Offer had been received in respect of a total of 43,039,745
AFA Shares, representing approximately 91.2 per cent of the existing issued
ordinary share capital of AFA.

As valid acceptances of the Offer have been received in respect of more than
nine-tenths in value of AFA Shares to which the Offer relates, Microgen intends
to apply the provisions of sections 428-430F of the Companies Act 1985 to
acquire compulsorily all outstanding AFA Shares on the terms of the Offer.
Accordingly, Microgen will be posting this week formal notices under section
429 of the Companies Act 1985 to AFA Shareholders who have not yet accepted the
Offer.

The Offer will remain open until further notice. As previously announced, the
Mix and Match Facility has closed.

The expressions in this announcement, unless the context otherwise requires,
bear the same meaning as in the Offer Document dated 18 August 2004 ('Offer
Document'). This announcement does not constitute an offer or an invitation to
purchase or subscribe for any securities. The Offer is made solely by the Offer
Document and the Form of Acceptance accompanying the Offer Document, which
contain the full terms and conditions of the Offer, including details of how
the Offer may be accepted.

The Offer is not being made, directly or indirectly, in or into, or by use of
mails or by any means or instrumentality (including, without limitation,
telephonically or electronically) of interstate or foreign commerce, or any
facility of a national securities exchange of, the United States, Canada,
Australia or Japan, and the Offer should not be accepted by any such use,
means, instrumentality, facility or otherwise from within the United States,
Canada, Australia or Japan. Accordingly, copies of this announcement, the Offer
Document and the Form of Acceptance are not being, and must not be, mailed or
otherwise distributed or sent in, into or from the United States, Canada,
Australia or Japan and persons receiving such documents (including nominees,
trustees and custodians) must not distribute or send them in or otherwise
forward, distribute, into or from the United States, Canada, Australia or
Japan. Doing so may render invalid any purported acceptance of the Offer.

The availability of the Offer to persons not resident in the United Kingdom may
be affected by the laws of their relevant jurisdiction. Persons who are not
resident in the UK should obtain their own advice and observe any applicable
legal and regulatory requirements.

The New Microgen Shares to be issued in connection with the Offer have not
been, nor will they be, registered under the Securities Act or under the
securities laws of any jurisdiction of the United States, nor has a prospectus
in relation to the New Microgen Shares been lodged with, or registered by, the
Securities Commission of any province or territory of Canada or the Australian
Securities and Investments Commission or the Ministry of Japan. Accordingly,
the New Microgen Shares may not be offered, sold, resold or delivered, directly
or indirectly, in or into the United States, Canada, Australia or Japan or any
other jurisdiction outside the United Kingdom in which the offer of New
Microgen Shares would constitute a violation of relevant laws or require
registration thereof.

UBS is acting exclusively for Microgen in connection with the Offer and no-one
else and will not be responsible to anyone other than Microgen for providing
the protections afforded to clients of UBS or for providing advice in relation
to the Offer or in relation to the contents of this announcement or any
transaction or arrangement referred to herein.

Enquiries:

Microgen plc

Mike Phillips (Group Finance Director)

Tel: [phone]

UBS Investment Bank

Nick Adams

Tel: [phone]

Financial Dynamics

Ben way

Tel:[phone]