Harlequins director of rugby Conor O'Shea has announced he will leave the club at the end of the current Aviva Premiership campaign.
The 45-year-old has been in charge at Twickenham Stoop since 2010 and he guided Quins to their first Premiership title in 2012.
The former Ireland full-back has also won the European Challenge Cup and the LV= Cup during his time with the club but he revealed this season would be his last.
"I will have been very fortunate to have had the opportunity to contribute to this special club for over six years come May," he told the club's official website.
"I have enjoyed working with everybody at Harlequins, from the players to the staff to the supporters, having said that, the end of this season is the right time for me to move on."
Harlequins are currently third in the Premiership table after nine games and are already through to the quarter-finals of the Challenge Cup after winning all five of their pool matches so far.
They head to Montpellier for their final pool game on Friday night and O'Shea, whose contract is due to expire at the end of this term, is determined to finish his six-year tenure in style.
"We have a very talented group of players and coaches who are intent on securing silverware this season and that is my sole focus and where all our efforts are concentrated," he said. "I will say my goodbyes when the season is over."
Quins will immediately begin the process of replacing the former London Irish boss but David Ellis, the club's chief executive, admits O'Shea will be a tough act to follow.
"All of us at the club are of course disappointed that Conor will be leaving us at the end of this season," said Ellis.
"Conor took over as director of rugby after a difficult period in our history. Under his leadership and through his determination, energy and positive approach he has helped restore pride in our famous shirt and rejuvenate the playing style for which we are known.
"His passion for the game, for the club and for the squad he has built is there for all to see.
"On behalf of all of us associated with Harlequins I would like to thank Conor for his tireless and selfless commitment over the last six years, guiding us through our most successful period on the field.
"Conor will leave the club in a significantly better place than he found us and for that we are all grateful to him.
"We all wish him and his family good fortune and every success in the future; there will always be a warm welcome for Conor at The Stoop."