Martin started his entertainment career as a stuntman but after breaking his collar bone filming the drama Elizabeth R he switched to acting. He featured in the BBC television series Paul Temple.
In 1978 he appeared as Detective Inspector Fred Pyle in The Detective's Tale, the first play in the BBC television series Law and Order. From 1981 - 82, he played Det. Insp. Berwick in two series of the BBC drama The Chinese Detective. In 1982 he became the second actor to take on the role of R. D. Wingfield's fictional Detective Inspector Jack Frost, starring in a BBC radio adaptation of A Touch of Frost. In 1984 he appeared in an episode of Minder, season 5. He then starred in Eldorado as Alex Morris. He has also made guest appearances in many television programmes including Doctor Who appearing in The Ambassadors of Death as an uncredited heavy, The Claws of Axos as an uncredited UNIT soldier and Image of the Fendahl as policeman David Mitchell, The Sweeney episode 'Messenger of the Gods' as the villain Spooner, Upstairs, Downstairs, The Bill and Only Fools and Horses. Martin also played himself in an episode of Little Britain.
In September 2000 he started playing Charlie Slater in EastEnders. In April 2010 it was announced that Martin had been cut from the show along with five other actors. In early 2011 he filmed a guest stint with EastEnders with Charlie due to return for two episodes around April 2011.