London - Harlequins and England back-row forward Nick Easter announced his retirement from rugby on Friday.
The 37-year-old will now take on a full-time coaching position with English Premiership side Harlequins, having become a player-coach with the London club in April.
"After accepting the opportunity of being a coach-player by (Quins director of rugby) John Kingston, I took some time to think about my career," Easter said in a Harlequins statement.
"I realised that whether I'm playing or coaching, there was no possible way that I would be able to give 100 percent to both of my roles at the same time."
He added: "I thought, why not grab the opportunity of becoming a coach with both hands, give it my best shot and feel privileged to be in a position to go out on my own terms after 12 great years as a player for Harlequins?
"I'm a few weeks into my role now and I'm thoroughly enjoying it. Having had five weeks in the off-season to finalise it and four weeks now as a coach, I don't regret my decision and I can't wait for the new season to begin."
Easter won 54 England caps for England, making his debut against Italy in the 2007 Six Nations.
In the same year the back-row forward played in the World Cup final defeat by South Africa and became the first England No 8 to score four tries in one match, during a 62-5 win over Wales.
After a prolonged absence from Test rugby, Easter was recalled by England for last year's Six Nations and then brought into the World Cup squad as an injury replacement for Billy Vunipola.
In England's final pool game at the World Cup, Easter became the oldest hat-trick scorer in Test history after crossing three times in victory over Uruguay - his final international appearance.
Easter also made 281 appearances for Harlequins since joining the club from Orrell in 2004 and in the process became Quins' most-capped professional player.
During his time at the Stoop, Easter helped Quins win the European Challenge Cup in 2011 and their maiden Premiership title the following year as well as the 2013 Anglo-Welsh Cup.
"Nick has been an unbelievable servant to the Harlequins team for over a decade," said Kingston.
"He has been at the very heartbeat of all the successes the side has achieved over this period."
Kingston added: "Nick has a fantastic rugby brain and it is for this reason I offered him the opportunity to join the new look coaching team at the club.
"Both Nick and I have agreed it is in the best interests of Quins that he focuses on his coaching exclusively from now."