Paul Gustard is to leave his role as England's defence coach in order to take over as head of rugby at Harlequins, the Premiership side have confirmed.
Gustard has been working with Eddie Jones' side since the start of 2016 and is regarded as one of the brightest coaches in English rugby.
The former Saracens assistant was a prominent member of a backroom team that steered England to successive Six Nations titles in 2016 and 2017, as well as series wins away in Australia and Argentina.
Gustard will continue with England for next month's tour of South Africa before taking up his new job at Quins.
Speaking to the club's official website, he said: "Opportunities like this don't come along very often. To be given the chance to lead a club as rich in talent, heritage and support as Harlequins is hugely exciting.
"I am a proud Englishman and it has been a privilege to represent my country and work under Eddie. There have been some incredible memories which I will cherish, and I will look back proudly on my contribution with England. I am desperate for England to do well as we push on to World Cup glory next year.
"My relationship with Eddie is strong and positive. He has supported me in accepting this new role and I will continue to have a strong relationship with him on our tour to South Africa and beyond. He was the first to give me an opportunity in 2008 and again in 2016 when he recruited me for England. I will always be thankful to him.
Harlequins Appoint England Coach Gustard https://t.co/BUqiruqAfC— Harlequins (@Harlequins) May 21, 2018
"However, I am now ready to lead a team and I am thrilled to have this chance at one of the Premiership's biggest clubs. I just couldn't turn this opportunity down. It is incredibly exciting to be part of the next chapter at Quins.
"I would like to thank the RFU and Eddie personally for their support and for allowing me to leave early to take up this fantastic opportunity with Harlequins."
Gustard's exit comes at a difficult time for England; they finished fifth in this year's Six Nations and are just 16 months away from the Rugby World Cup.
Wales' defence coach Shaun Edwards, who reportedly interviewed for the Quins post, has been mentioned as a possible replacement on Jones' staff, although he is also thought to be considering a return to rugby league.
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