Harlequins director of rugby Conor O'Shea has insisted Tom Guest will always be welcome back at the Stoop after the number eight confirmed a switch to London Irish for next season.
The 29-year-old former England Saxons and Sevens international has called time on a 12 year stay at the club he joined as an 18-year-old and for whom he has made more than 200 appearances and scored 26 tries.
"Tom has been one of Harlequins' great servants having recently celebrated his 200th game," said O'Shea.
"I know he is committed to going out on a high this season with the club that will always be his.
"We would love to have kept Tom for his entire career, but the nature of managing a squad within the imposed salary cap regulations involves both accounting for the players you already have and developing personnel within each position.”
Guest made his senior debut in 2005 and was part of the squad that lifted the LV= Cup in 2013, Premiership title in 2012 and the Amlin Cup in 2011.
He added: "I have been at Quins for 12 years and had a great time throughout.
"I'd like to thank all the coaches and everybody at the club, with a special mention to Collin Osborne who has been there for me since I was 18 and has done so much for me.
"It was a really hard decision to go, but I am looking forward to the next stage of my career and a new challenge at London Irish.”