Born Russell Ellis in Glasgow, Hunter's childhood was spent with his maternal grandparents in Lanarkshire, until returning to his unemployed father and cleaner mother when he was 12. He went from school to an apprenticeship in a Clydebank shipyard. During this time, he did some amateur acting for the Young Communist League before turning professional in 1946.
His most memorable role was the timid, smelly petty criminal, Lonely, unlikely accomplice to a clinical spy-cum-assassin, in the downbeat 1967 television spy series Callan. Reportedly, he said of his identification with Lonely that "I take more baths than I might have playing other parts. When Lonely was in the public eye I used only the very best toilet water and a hell of a lot of aftershave." After playing Costard in a BBC television production of Love's Labour's Lost, Hunter was cast as Lonely in ITV's "Armchair Theatre" production A Magnum for Schneider in 1967, which introduced the secret agent Callan to the screen. Four series followed. Hunter and Edward Woodward reprised their roles in both a 1974 feature film of the same name and, seven years later, in the television filmWet Job, by which time Lonely had gone straight, got married and was running a plumbing company called Fresh and Fragrant. The title plays on "wet job" the euphemism for murder or assassination.
Other roles
During his years with Callan, Hunter acted in the Hammerhorror filmTaste the Blood of Dracula and took the roles of Crumbles, Dr Fogg and Dr Makepeace in an ITV production of Sweeney Todd, He also appeared in the British comedy filmUp Pompeii as the Jailer. He had two notable appearances in one-man plays performed on BBC Scotland in the early 1970s: Cocky, where he played Henry Cockburn, Lord Cockburn, which ended with his speech to the jury defending Helen McDougal, Burke's wife, in the Burke and Hare case, and Jock, where he played an archetypal Scottish soldier guarding a military museum. In 1974 he played Ted, a simple-minded but kind-hearted man in a two-part story in Rooms , two-part dramas concerning the various drifters who rent rooms in a lodging house. In 1975 he played a Scottish painter in the BBC's adaptation of the Lord Peter Wimsey story The Five Red Herrings. In 1979, at the artist's request, he opened the Edinburgh Festival Exhibition of the Glasgow artist Stewart Bowman Johnson held at the Netherbow Gallery. Hunter's other TV credits include The Sweeney, Ace of Wands, Doctor Who: Robots of Death, Farrington of the F.O., The Bill, A Touch of Frost, Taggart, sitcoms Rule Britannia as the Scotsman Jock McGregor and shop steward in The Gaffer, and his last ever TV appearance, in the BBC drama Born and Bred. In his last years he reprised his Doctor Who role for a series of audio plays released on CD, Kaldor City. He also appeared in an episode of Mind Your Language as a minor character in the episode "I Belong To Glasgow". He also appeared in the TV sitcom Lovejoy as a Scottish submariner in the episode "Angel Trousers". He also appeared as different characters in the pilot and series of the BBC sitcom Rab C. Nesbitt.
Although in the advanced stages of cancer, Hunter's last theatrical stint was in the Reginald Rose play 12 Angry Men at the same, if inconceivably expanded, Edinburgh Festival Fringe, with which he had remained inextricably linked. Despite being ill, Hunter received positive reviews for his appearances in the feature film American Cousins late in 2003 and as a priest in the film Skagerrak. In November, American Cousins, Hunter's last movie role, received the Special Jury Prize at the Savannah Film Festival in the United States, ending a career spanning six decades.