Paul Gustard has left his role as England defence coach to become the new head of rugby at Harlequins.
It was confirmed on Monday afternoon that Gustard had agreed to join the Aviva Premiership club following England's June tour of South Africa.
The move is a considerable blow to England coach Eddie Jones, who will be forced into a coaching reshuffle just 16 months out from the 2019 Rugby World Cup in Japan.
However, Gustard insisted that he had taken up Harlequins' offer with the backing of the national team boss.
"Opportunities like this don't come along very often," Gustard said in a statement issued by Harlequins.
"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."
Jones paid tribute to Gustard as he commented on his appointment: "I wish Gussy [Gustard] all the best at Quins. He is a talented young English coach and a very good choice for the role.
"He has made a big contribution to the England coaching team as our defence coach and I'm happy that he has this opportunity to develop and prove himself in a head coach role."
Harlequins had been on the lookout for a new boss since it was announced in April that John Kingston would leave his role as director of rugby following a disappointing season.
The London club took the decision to restructure its management team and will appoint a general manager to work alongside Gustard in due course.
Gustard will have sole responsibility for day-to-day coaching at the club, while the general manager will be tasked with off-the-field duties such as player and coach recruitment.
It is understood that Wales defence coach Shaun Edwards and former Fiji Sevens boss Ben Ryan were both also shortlisted for the head of rugby position.
"We were determined to recruit a coach with a proven track record in delivering a winning team and environment, and we have done that," Harlequins chief executive David Ellis said.
"Paul has extensive experience at the highest levels with Saracens and England and is one of the most respected coaches in world rugby."