Born in Tonga, he started his career in league with the Canberra Raiders before making his name in this country with the Bradford Bulls where he scored 149 tries in 152 appearances.
He joined Gloucester Rugby in time for the start of the 2007-8 season and couldn't have made a more spectacular start to his career in union as he scored five tries against Leeds Carnegie at Headingley on his debut.
He was soon drafted into the England international set up, making his debut against Wales at Twickenham in February 2008 and going on to win five caps in total.
His career at Gloucester saw him become a massively popular figure with the Kingsholm faithful and his impact is reflected by the 36 tries that he scored in 86 competitive starts.
Head Coach Bryan Redpath paid tribute today to Vainikolo and explained the reason for his departure.
"No one can deny the impact that Lesley has had on Gloucester Rugby and on the English game in general.
"He adapted from league to union in no time at all and could always be relied upon to give 100% whether in his preferred position on the wing or in the centre when we asked him to.
"La Rochelle approached us to ask permission to talk to Lesley and explained that they were prepared to offer him a two and a half year contract if we were willing to allow him to leave immediately.
"Lesley has been a fantastic servant to Gloucester Rugby and, frankly, it would have been unfair of us to stand in his way. He travelled there this week for a medical and to discuss terms and it's a great opportunity for him.
"He goes with our best wishes and our thanks. He'll always be remembered here at Kingsholm and will always be welcome."