Jérôme Kerviel, the rogue trader accused by Société Générale of fraud that eventually cost the bank €4.9bn ($7.3bn), has testified that his superiors were aware of his huge positions but turned a blind eye as long as they were profitable.

"I can't believe that my superiors were not aware of the amounts I was committing. It's impossible to generate such profits with small positions," Kerviel said in court yesterday.