Castaignede, a gifted attacking talent at fly-half, centre or full-back, joined Saracens from French club Castres in 2000, but he has decided not to pursue a new contract with the Guinness Premiership club.

"I knew at the start of the year that this would be my last season," Castaignede told The Guardian newspaper.

"My years in England have allowed me to experience a different style of rugby, a new culture and some fine people."

Castaignede's final Saracens appearance came in the 50-9 Premiership play-off defeat against Gloucester at Kingsholm last Saturday, but he is to remain based in north London as he concentrates on a career in banking.

Before joining Saracens, he helped Toulouse land four French titles and the Heineken Cup.

He added: "I hope I will go to the World Cup, and then I will stop afterwards. But there are no certainties for anyone, there are several stages to get there.

"However, I will keep training flat out. Mentally and physically, I want to be ready."