Further to the announcement released by Northern on 3 April 2009 in accordance with rule 2.5 of the Takeover Code (the “2.5 Announcement”) the Independent Northern Directors and the Independent ATI Directors are pleased to announce, in accordance with rule 8.4 of the Takeover Code, that in addition to the irrevocable undertakings referred to in the 2.5 Announcement, Northern has now received further irrevocable commitments from the following person to vote in favour of the resolutions to be proposed at the Court Meeting and the General Meeting to implement the Proposals:

Barry Lonsdale, who previously was the beneficial owner of the above shares, is now the legal owner of the shares and as such the irrevocable commitment signed by him and referred to in the 2.5 Announcement now becomes effective over these additional 1,200,000 shares.

The above irrevocable commitment will continue to be binding in the event that the Proposals are implemented by way of a takeover offer and in the event of a higher competing offer for ATI.

Accordingly, Northern has now received, in aggregate, irrevocable commitments to vote in favour of the resolutions to be proposed at the Court Meeting and the General Meeting to implement the Proposals in respect of 48,428,000 ATI Shares, representing approximately 51.4 per cent. per cent. of the current issued share capital of ATI or 81.6 per cent of the current issued share capital of ATI not controlled by members of the Northern Group.

Terms used in this announcement have the same meaning as in the 2.5 Announcement.

For further information please contact:

Northern Petroleum Plc
Tel: +44 (0) 20 7469 2900
Derek Musgrove, Managing Director
Chris Foss, Finance Director
Graham Heard, Exploration & Technical Director

Investec (NOMAD and Financial Adviser)
Tel: +44 (0) 20 7597 5000
Michael Ansell / Patrick Robb

The directors of Northern accept responsibility for the information contained in this announcement. To the best of the knowledge and belief of the directors of Northern (having taken all reasonable care to ensure that such is the case) the information contained in this announcement is in accordance with the facts and does not omit anything likely to affect the import of such information.

This announcement will shortly be published in accordance with Rule 19.11 of the Takeover Code on Northern’s website, http://www.northpet.com, in the news section.

Dealing Disclosure Requirements

Under the provisions of Rule 8.3 of the Takeover Code, if any person is, or becomes, 'interested' (directly or indirectly) in 1% or more of any class of 'relevant securities' of the Company or ATI, all 'dealings' in any 'relevant securities' of that company (including by means of an option in respect of, or a derivative referenced to, any such 'relevant securities') must be publicly disclosed by no later than 3.30 pm (London time) on the London business day following the date of the relevant transaction. This requirement will continue until the date on which the offer becomes, or is declared, unconditional as to acceptances, lapses or is otherwise withdrawn or on which the 'offer period' otherwise ends. If two or more persons act together pursuant to an agreement or understanding, whether formal or informal, to acquire an 'interest' in 'relevant securities' of the Company or ATI, they will be deemed to be a single person for the purpose of Rule 8.3.

Under the provisions of Rule 8.1 of the Takeover Code, all 'dealings' in 'relevant securities' of the Company or ATI by the Company or ATI, or by any of their respective 'associates', must be disclosed by no later than 12.00 noon (London time) on the London business day following the date of the relevant transaction.

A disclosure table, giving details of the companies in whose 'relevant securities' 'dealings' should be disclosed, and the number of such securities in issue, can be found on the Takeover Panel's website at www.thetakeoverpanel.org.uk.

'Interests in securities' arise, in summary, when a person has long economic exposure, whether conditional or absolute, to changes in the price of securities. In particular, a person will be treated as having an 'interest' by virtue of the ownership or control of securities, or by virtue of any option in respect of, or derivative referenced to, securities.

Terms in quotation marks are defined in the Takeover Code, which can also be found on the Panel's website. If you are in any doubt as to whether or not you are required to disclose a 'dealing' under Rule 8, you should consult the Panel.

Investec Investment Banking, a division of Investec Bank plc ("Investec"), which is authorised and regulated in the United Kingdom by the FSA, is acting for Northern and for no-one else in connection with the Proposals and the matters referred to in this announcement and will not be responsible to anyone other than Northern for providing the protections afforded to customers of Investec or for providing advice in connection with the matters set out in this announcement.