The terse announcement, slipped out just before Christmas, about the departure of the head of a medium-sized French investment bank was hardly a show-stopper in the context of tens of thousands of job cuts in an exhausted investment-banking industry.

But when you consider that the bank involved was Societe Generale, which has had its moments in investment banking and which is struggling to retain the confidence of investors, it is worth digging a little deeper. And the closer you look, the more it appears that, far from being a simple change in leadership at the top of SocGen's corporate and investment bank, there has been a wholesale changing of the guard, if not a palace coup.