London Irish have confirmed that Sean O'Brien will join them after the World Cup.
The Leinster back row turns 32 later this week, and will link up with the English Championship leaders in December.
O'Brien will work under Declan Kidney, the man who gave him his first Ireland cap a decade ago.
The Ireland flanker says it was a conversation with Kidney that convinced him of the club's ambitions.
During his time with Leinster to date, O'Brien has won four Heineken Champions Cups and a pair of Pro 14 titles.