Deferred Share Bonus Plan

Costain Group PLC("Costain" or "the Company")

Deferred Share Bonus Plan

This notification is made in accordance with DTR 3.1.4(1)(a).

On 12 April 2011, awards over ordinary shares in the Company were made to certain directors of the Costain Group PLC (the "Company") under the Costain Deferred Share Bonus Plan (the "Plan").

The awards granted under the Plan are structured as an option with a nil exercise price over a number of shares ("Deferred Award"). No consideration was paid for the grant of the Deferred Award.

The Deferred Awards will become exercisable on the second anniversary of the date of grant subject to the continued employment of the participant. To the extent that all or any part of a Deferred Award becomes exercisable, it remains exercisable until the tenth anniversary of the date of grant.

The Company was informed of the above transactions under the Plan on 12 April 2011.

 14 April 2011