19 May, 13:05
"I would like to thank Bath for their support, I have enjoyed my time with them and take found memories away with me," said the South African.
"The Lions vision excites me and I am also very keen to be part of the Springboks for the World Cup this year.
Head coach Steve Meehan was disappointed to be loosing a player of James' calibre.
"He is a very talented player, and so we are disappointed to seem him leave at the end of the season," said Meehan.
"He has been a great squad member, both on and off the pitch, and an inspirational player in so many ways and I have no doubt that he will play a very important role for us in the remainder of our games".