Bowling coach Stuart Barnes has left Gloucestershire to team up with former County skipper Jon Lewis at Surrey.
Barnes was a player at Nevil Road between 1989 and 1991 and returned in 1997 as a recreational cricket coach.
He has since filled the roles of academy director and second XI coach before joining director of cricket John Bracewell's first-team staff.
Bracewell said: "It is with regret and sadness that we see the departure of Stuart.
"He has been at the club for a long time, serving as a player then community coach and latterly as my assistant and bowling coach.
"It is as a bowling coach that Stuart has really shone, guiding many of our young pace bowlers through to becoming formidable first class cricketers.
"This has undoubtedly been our strength in the last seven to eight years. Stuart will be missed by both players and staff."
Barnes said: "I've thoroughly enjoyed working as fast bowling coach for Gloucestershire in the last few years.
"The flexibility shown by the club on a regular basis, and most recently allowing me to gain experience coaching in Bangladesh, as well as with England Lions, will prove invaluable as I look to continue moving forwards with my career."