Can banks run investment banks? This has not been a good week for a number of proud European institutions that have expanded into more exotic areas of finance. Credit Suisse was embarrassed, only a week after publishing its results, to announce that it had "identified mismarkings and pricing errors by a small number of traders" to the tune of $2.85bn. Société Générale, meanwhile, was criticised by a report into Jérôme Kerviel's €4.9bn trading loss. It raises the fundamental question of whether commercial banks have the right culture to manage risk-taking traders.

Commercial and retail bankers are like battery hens. You put them in a small cubicle, pressurise them with tough sales targets but provide a decent salary, and they will produce a steady stream of returns. Most are conservative, somewhat harassed souls, who seldom think to bite the hand that feeds them.