Walker made his professional acting debut in 1983 on stage in London playing an East End punk rocker in the musical Labelled with Love, based partly on the music of the pop band Squeeze. His first television appearance came in 1985 when he appeared in an episode on the second series of Dempsey and Makepeace, which aired on ITV on 19 October 1985. His next television appearance came the following year in an episode of the children's anthology series Dramarama, also on ITV. Also that year, he was cast in the role of Winston, a black, gay, council carer and a thorn in Alf Garnett's side, for series 1–3 of In Sickness and in Health on BBC One. In 1987 he appeared in an episode of Bulman on Granada TV and in 1988 an episode of the ninth series of Tales of the Unexpected. In 1988 he won the role of PC Malcolm Haynes in The Bill on ITV, a part he played from 1988–89.