Walker's earliest television role was as a policeman in the British "The Wednesday Play", in the episode titled "Fable" (aired 27 January 1965). He is known for his comedic roles in "Love Thy Neighbour" (Thames Television), "The Thin Blue Line", which starred Rowan Atkinson, and in "Ali G Indahouse". He also appeared in "Doctor Who", in the 1969 serial "The War Games", and also in several episodes of "Empire Road" in 1979. He was one of the first black actors to be seen regularly on British television, and so has always been proud of his role on the controversial "Love Thy Neighbour", which ran for seven series, from 1972 to 1976.