As Midas discovered, a fixation with wealth has its hazards. Investment banks should take note. With the credit crunch proving how painfully cyclical many parts of investment banking can be, many chief executives are looking towards their wealth management arms, perceived as a more stable business, to keep cash flowing. Yet the glitter of private banking is not all it appears.

There are some economies of scale. Central costs are spread over a broader base. Close relationships with oligarchs, for example, may generate corporate advisory business. But private banking remains very much a high service and, therefore, costly proposition. A single private banker looks after only about 50 clients.