John Leeson is best known for voicing K-9 on Doctor Who from 1977 to 1979, then from 1980 to 1981, and has returned for two single episode in the revived series. He also voiced K-9 in the show's spin-offs K-9 and Company, The Sarah Jane Adventures and K-9. He also voiced the Nucleus in "The Invisible Enemy," played Dugeen in "The Power of Kroll," voiced the Dalek battle computer in "Remembrance of the Daleks" and played Anthony in the Reeltime Pictures spin-off video Downtime. Other credits include appearances in Blake's 7 (season B episode "Gambit"), Jigsaw in which he played the giant Biggum, who was so tall only his feet were seen and his voice heard, Sorry!, 'Allo 'Allo! and Bungle in the children's television series Rainbow, and recently was a continuity announcer on Britain's Channel 4.