Trading Update

Costain Group PLC

("Costain" or "the Group")

Pre-Close Trading Update

Since the announcement of the Group's Interim Management Statement on 5 May 2011, Costain has continued to perform well and is trading in line with the Board's expectations.

Against a backdrop of well-publicised uncertain market conditions, the Group has continued to implement its strategy successfully and has secured contracts from its blue chip customers in chosen sectors whose major spending plans are underpinned by strategic national needs, regulatory commitments or essential maintenance requirements.

Consequently, the Group's order book currently stands at £2.3 billion, with additional preferred bidder positions of over £400 million. As at the end of the first half, over £900 million of revenue has been secured for 2011.

The level of tendering activity in the Group's targeted markets of Infrastructure, Environment and Energy & Process remains high.

Costain has maintained its strong cash position in excess of £100 million, and has no significant borrowings. In addition, in order to support the delivery of its strategy, the Group has recently increased its total banking and contract bonding facilities by £90 million to £435 million.

The Group announced in April 2011 the acquisition of ClerkMaxwell Limited, an Aberdeen-based front-end engineering and operations support services provider operating in the upstream oil & gas sector. The integration of ClerkMaxwell into the Group is proceeding smoothly and the business is trading well.

Costain will announce interim results for the six months ended 30 June 2011 on Thursday 25 August 2011. There will be a presentation to analysts at 9.30am on that date at the offices of College Hill: The Registry, Royal Mint Court, London, EC3.

30 June 2011

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