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.
22. September 2018
|Rose not changing approach alongside Woods|
|Woods ready to ´hang in there´ at East Lake|
|Shaqiri´s time will come at Liverpool – Klopp|
|Richarlison: I used to copy some of Neymar´s haircuts|
|Brady says Gordon is ´really eager to get in there´ despite limited practice|
|NBA changes clock-reset, ´clear path´ foul rules|
|Tigers´ Martinez will play final game on Saturday before retiring|
|Sanchez to start for Man United – Mourinho|
|Speight saves Ulster in thrilling Cheetahs draw|
|Simmonds at the double as Chiefs stay perfect|
|Woods, Rose share Tour Championship lead|
|Ice-cool Shoaib denies Afghanistan in final over|
|CAF Champions League Review: Wydad Casablanca out as TP Mazembe pay penalty|
21. September 2018
|Eden inspires rout as Castleford book Wigan semi-final|
|Thiem & Wawrinka reach St. Petersburg semi-finals|
|No change to Aguero selection despite new contract, warns Guardiola|
|Woods and Rose share Tour Championship lead|
|Wigan Athletic 1 Bristol City 0: Three on the trot for improving Latics|
|Josh Rosen will play ´when time is right,´ Cardinals GM says|
|Eagles RBs Ajayi & Sproles out Sunday v Colts|
|Ronaldo looking forward after Champions League red card - Alex Sandro|
|Rangers fire manager Jeff Banister after four seasons|
|Inter captain Icardi can improve - Spalletti|
|Jadeja and Rohit shine as India maintain 100 per cent record|
|Fisher shares lead in Vilamoura after record-breaking 59|
|Messi the best I´ve seen - Lamela|
|Silva demands end to Gomes ´rumours´ and targets early October return|
|Milner over Pogba, says Souness|
|Brazil call up Malcom, drop Thiago Silva and Willian|
|Denly thought Test chance may never come|
|Benitez tells FA to examine Zaha red card comments|
|Bjorn unsure of future after Ryder Cup|
|Tebas still optimistic over Girona-Barcelona in Miami despite RFEF setback|
|Emery promises more chances for frustrated Leno|
|Cahill considering Chelsea departure in January|
|Kaepernick to receive Harvard´s highest honour in African, African-American studies|
|Defending champion Ostapenko dumped out of Korea Open|
|Mourinho is an inspiration - Nuno|
|Witty Wilson ´delighted´ to be praised for Fisher heroics while sitting on couch|
|Burns, Denly and Stone in England squad for Sri Lanka Tests|
|Aspas reveals interest from Real Madrid, Atletico|
|Arsenal´s Mkhitaryan a doubt for Everton match|
|Klopp demands Liverpool ´stay angry´ against Southampton|
|Long-serving Tabarez signs four-year Uruguay extension|
|Injured Mendy ruled out of Cardiff trip|
|Douglas Costa out up to a month with ankle & thigh injuries|
|Slater shrugs off Feki hit amid Grand Final suspension concerns|
|Crisis? What crisis? Klopp unconcerned by Salah form|
|I didn´t convince him, he decided for himself - Guardiola says thanks to Aguero|
|Leno frustrated by Arsenal bench role|
|Joshua almost 2st heavier than Povetkin for Wembley bout|
|From salvation to the record books - Fisher revels in European Tour´s first 59|
|Lahm says Germany best for Euro 2024 as UEFA publishes report|
|Lopetegui backs Modric over Ronaldo for individual prizes|
|Goretzka to start against former club Schalke, confirms Kovac|
|Fisher shoots first 59 in European Tour history|
|Simeone defends Ronaldo after controversial Champions League red|
|Slater sees Storm into Grand Final, awaits fate over ´shoulder charge´|
|Hogg to miss Scotland´s November Tests following ankle surgery|
|Osaka through as Azarenka and Garcia crash out|
|Burgess weighing up legal options after being cleared in Rabbitohs investigation|
|Uncapped Cottrell and Gordon named in Wallabies squad|
|He´s done fantastic work - Mourinho hails Wolves boss Nuno|
|Joshua v Povetkin: No need for fireworks on AJ´s Wembley return|
|Six titles, 204 goals - Aguero´s incredible City career in Opta stats|
|Read to miss Argentina clash, Ioane brothers sign new deals|
|Pedro allays injury fears after Europa League clash|
|Dilly dilly to all the Cleveland fans! Mayfield promises further Browns success|
|Manchester United ´hell´ left Zaha depressed|
|Jackson hesitates in naming Mayfield as Browns´ starting QB|