He has been employed by Celtic for more than forty years over eight decades, since signing as a player in 1958, then having spells as a coach, assistant manager and currently kit controller.
The arrival of Jock Stein as manager in 1965 saw Clark moved from left half to a sweeper position behind Billy McNeill.
His undramatic style of play beside fellow centre back McNeill was integral to the success of the team; his role as Celtic's sweeper earned him the nickname "The Brush."
Clark then worked as manager of Cowdenbeath, Stranraer and Clyde, as well as junior club Shotts Bon Accord, in the 1980s and early 90s.
His son Martin also became a professional footballer, playing with Clyde, Nottingham Forest and Partick Thistle in the 1990s.