Kerviel’s massive market bets brought French bank Societe Generale close to collapse in 2008, but the former trader has always insisted his bosses knew what was going on. He was convicted of breach of trust, forgery and fraudulent data manipulation.
Several appeals against his sentence – most recently in March – have failed, but France’s highest court quashed a €4.9bn (£4bn) fine that Kerviel had been ordered to pay in compensation.
Kerviel, 37, has been walking from Rome to France in a so-called march against the markets. On Saturday he stopped his journey in Ventimiglia and told reporters he wanted to talk to French President Francois Hollande. But he walked into France just before midnight on Sunday, and was detained in a police station until his arrest yesterday morning.