Stewart developed an interest in acting at the age of 12, participating in local drama groups. At 17, he was accepted into the prestigious Bristol Old Vic Theatre School, where he trained professionally. He made his first professional stage appearance in 1959 with a repertory company in Lincoln. In the early 1960s, he toured internationally with the Old Vic Company. In 1966, Stewart joined the Royal Shakespeare Company, initiating a long-standing association that would last nearly three decades.

Transition to Television and Film

After earning critical acclaim for his stage work, including a Laurence Olivier Award for Best Actor in a Supporting Role for his performance in Antony and Cleopatra in London’s West End, Stewart began expanding into television and film. Although his early television appearances in the late 1960s were limited to minor roles, he gained broader recognition in the 1970s with performances in British Broadcasting Corporation (BBC) productions such as I, Claudius and Hedda.

Notable television roles during this era include Vladimir Lenin in Fall of Eagles, Sejanus in I, Claudius, and Karla in both Tinker Tailor Soldier Spy and Smiley’s People. Stewart also appeared in films, including portrayals of King Leondegrance in John Boorman’s Excalibur (1981), Gurney Halleck in David Lynch’s adaptation of Dune (1984), and Dr. Armstrong in Tobe Hooper’s Lifeforce (1985).