His television credits include The Saint, Counterstrike, The Borderers, Codename, Colditz, The Zoo Gang, The Sweeney, Warship, Doctor Who (in the serial The Hand of Fear), Survivors, The New Avengers, Space: 1999, The Professionals, Secret Army, Van der Valk, Blake's 7, Minder, Dempsey and Makepeace, The Bill, Heartbeat and New Tricks.
In 1974 Boyd had a principal guest role in lunchtime series Emmerdale Farm in which he played a mysterious tent-dwelling camper who many villagers felt had anarchist tendencies.
In fact the character, Dryden Hogben, was warm, intelligent, and ended up living with the Sugdens for some time.
From 1980 to 1983, Boyd had a recurring role as criminal Eddie Lee in the long running soap opera Crossroads.
His film credits include appearances in The Wicker Man (1973), The Omen (1976), A Nightingale Sang in Berkeley Square (1979), Biggles (1986) and Asylum (2005).