After leaving school, John Leeson worked in a bookshop, and then as a porter in the Leicester Royal Infirmary Hospital. He joined the Leicester Dramatic Society and ultimately applied for and won a place at RADA. On leaving the Royal Academy of Dramatic Art, he worked in repertory and pantomimes, including "Toad of Toad Hall," in which he met his future wife. His first work in television was as a walk-on in a BBC play, "The Wedding Feast." "The Spanish Farm" (1968), "Dad's Army" and numerous situation comedies followed. He played the original Bungle the bear in the children's series "Rainbow" (1972), set questions for "Mastermind" and did a lot of freelance voice work for the BBC. The part of K-9's voice came his way after he bumped into the director, with whom he had worked previously, in a pub. Since his time in "Doctor Who," Leeson has continued to act and provide voiceover services for the BBC and many other companies. In 1995 he appeared in the "Doctor Who" spin-off video drama "Downtime," playing a disc jockey.