Aitken attended Belmont Abbey School and the St. Mary's University College in London, where he trained as a drama teacher. By the early 1970s he had first guest roles in television series such as The Upstairs Downstairs, Z Cars and code name Seeney. In 1977, he starred in the six-part series London Belongs to Me, and 1979-1980 he had the lead role in the sitcom End of Part One. In the same year he played a guest role as speaking English hitman from simmering in the Austrian crime series Kottan determined. In the second season of Rowan Atkinson's Blackadder, he had a recurring role.
His feature film credits include small roles in Terry Gilliam's Jabberwocky and eight -time Academy Award - nominated film drama What Remains of the Day. Aitken runs a recording studio, where he produced radio and television commercials.