How many golden opportunities have been missed? As share prices tumble, companies that have rejected takeover bids in the past two years are looking foolish. Investors can feel aggrieved. But the truth is that shareholders are sometimes equally guilty of making the wrong call.

Boards must often take the blame. Yahoo’s shares are not only below Microsoft’s rejected $33-per-share offer, but have underperformed their global peers by a fifth since the deal was first proposed. Informa, the UK-based business and academic publishing group, spurned a 630p-per-share offer from Springer Science and Business Media in October 2006. Its shares are now trading at 415p and would be lower still without another supposed bidder in the wings. Sometimes the facts are less clear cut. Since Prudential’s board cold-shouldered Aviva, its domestic rival, its shares have fallen 20 per cent below the offer price. But they have, at least, outperformed Aviva’s since the bid was announced in March 2006.