The giant universal banks are riddled with conflicts of interest. If you want unbiased advice on mergers and acquisitions, much better to go to an independent advisory firm. Right? Er, not entirely.

The worry is that banks and bankers make so much money out of big deals that they can forget the interests of their clients. The temptation is to push the deal even if there is a good chance it will prove a loser for the client in the long term. For big banks, the reward comes not just from the advice but from a package of other, often more lucrative, services, such as financing.