Many bankers would have nodded in agreement last year when Bank of America chief executive Ken Lewis said prime broking was about as sensible an activity to be involved in as walking onto the fast lane of a motorway to pick up a small coin.

Redemptions and deleveraging in the hedge fund industry suggested the business would become far less lucrative for banks. Some, most notably Morgan Stanley, even spoke publicly about downsizing in prime broking, a business that consumes significant amounts of a bank's balance sheet.