Ireland international Eoin Reddan is to leave London Wasps after four seasons to join Heineken Cup semi-finalists Leinster.
The scrum-half moved to Wasps from Munster in 2005, helping them win the Heineken Cup, Guinness Premiership and Powergen Cup during that time.
He also made his international breakthrough while at Wasps, being handed a Test debut against France in 2006 and going on to win 14 caps.
Wasps rugby director Ian McGeechan said: "We are obviously sad to see the departure of Eoin Reddan, a player whose talent and fantastic attitude have played a key role in our success over the last four seasons.
"We are, and always will be, a club that supports our players' international ambitions however, and it is with our blessing and support that we see him head back to Ireland and join Leinster, pushing for honours on both the domestic and international stage.
"It has been a pleasure to work with a player of Eoin's calibre, and he will be missed by all at the club."
Reddan added: "It is tough for me leaving Wasps. I've thoroughly enjoyed my last four years and I can't overstate how great a club it is.
"The fitness team, physiotherapy staff and backroom team are top class and make it easy for you to be at your best week in, week out in what is a long season.
"The coaches have helped me personally and supported me over the last four years, and I would like to thank them for all their help and support, particularly in my decision to go home to look to further my international career."
England's preparations for the Autumn International series were potentially dealt a further blow as Maro Itoje was forced to undergo an x-ray after Saracens' European victory over Scarlets on Saturday night.