A good spring clean is always cathartic. Nowhere more so than at investment banks, which in the first few months of 2012 collectively took out the scrubbing brush, got down on their hands and knees, and spruced up their numbers.

The main reason for this overdue housework was the combination of a downturn in activity and the regulatory equivalent of a cleaning inspection, with banks having to set aside more capital against their trading operations. This, in turn, forces them to spruce up their balance sheets and cut costs. Yet, even at those banks whose spring clean resembled the work of Hercules in the Augean stables, the results are far from sparkling.