Iconic projects seem to act as a tonic for Costain, the construction group. Best known for its involvement with the Channel Tunnel in the early 1990s, it was not until its St Pancras Eurostar terminal was unveiled last year that the company resumed dividend payments after 17 years. Now Costain looks to be going from strength to strength. Its £2bn order book is bound to be boosted by upcoming sites, including the £16bn Crossrail build, £70bn-worth of nuclear work and the 2012 Olympics. Costain's improving position needs to be matched with a rise in margins if it is to be rated more highly than a sector average of 10 times forecast earnings. But an abundance of work and a robust balance sheet suggest a rating higher than its 6.8 multiple. Some parts of the business look vulnerable to a downturn, but not enough to justify a 30 per cent discount to peers. If the markets don't see the intrinsic value, a trade buyer might.