“I don’t know where he is,” said Daniel Bouton, the long-standing chief executive and chairman of Société Générale, when he was asked on Thursday about the whereabouts of Jérôme Kerviel, the trader at the centre of one of the biggest frauds in banking history.

But while Mr Kerviel’s movements remained unknown, the sequence of events that led to the extraordinary writedown at SocGen was becoming clearer.