Chief executive Andrew Wyllie’s plan to transform Costain into an engineering solutions business through the acquisition of several firms has already started to change the work profile.

Now more than a quarter of all revenue comes from higher value consultancy and maintenance work.

The completion of poor performing contracts saw revenues dip 12% to £468m. But the change in mix of work at Costain lifted profits by 23% to £10.1m in the six months to the end of June.

The uplift in performance from its environment division failed to be mirrored at the infrastructure and energy divisions where profits fell.

Costain has built up a strong cash balance of nearly £150m and an order book of £2.3bn.

Around £900m of revenue has been secured for 2011 at the half year. A further £500m revenue is in place for 2012.

Costain’s  order book also provides good long-term visibility with over £1.3bn of revenue secured for 2013 and beyond.

Chairman, David Allvey, said: “We are delighted with another strong set of results, with a significant increase in profit before tax, an enhanced cash balance, and a robust order book including further new contract awards from our major customers.

“The implementation of our ‘Choosing Costain’ strategy is transforming the group, as we continue to develop or acquire the skills and capabilities to reinforce our position as one of the UK’s leading tier one engineering solutions providers.

“Looking ahead, despite continuing challenging market conditions, we see significant opportunity for the continued successful implementation of our strategy and the delivery of the board’s ambition of doubling profit over the medium term.”