Sean O'Brien: Ireland and Leinster flanker to join London Irish in December
Ireland and Leinster flanker Sean O'Brien will join London Irish in December following the World Cup.
It was reported last week that 31-year-old O'Brien was set for a move to the Championship leaders and the switch was confirmed on Monday.
O'Brien will join up with former Ireland head coach Declan Kidney and Les Kiss at the club.
He said: "I'll roll up the sleeves and use my experience to re-establish London Irish as a top club in England."
"After speaking with Declan it was obvious the ambition London Irish have as a club," added O'Brien, who is a two-time British and Irish Lions tourist.
"It's a club that's been around for a long time and there's an obvious connection to Ireland with some greats of Irish rugby having previously worn the jersey.
"For now my concentration remains solely with Leinster and Ireland but it's an exciting challenge that awaits."
The move is unlikely to affect O'Brien's World Cup prospects as he is centrally contracted to the Irish RFU until the conclusion of the tournament.
O'Brien's situation is similar to Paul O'Connell before the 2015 World Cup - when the then Irish captain had agreed before the tournament to join Toulon.
However, while there is no official policy regarding the selection of players based outside Ireland, it is unlikely O'Brien will be considered for the 2020 Six Nations by Andy Farrell, who will replace Joe Schmidt as Ireland head coach after the World Cup.
Former Munster fly-half Ian Keatley and former Ireland Under-20 duo Conor Gilsenan and Brendan Macken are currently on the books of London Irish.