He is also known for his role of the level-headed widower Norman Clegg in the BBC sitcom Last of the Summer Wine, which he has played since 1973. However, his long career has included many other stage, film and TV appearances.
After attending Minchenden Grammar School in North London, Sallis started as an amateur actor in the RAF during World War II. He failed to get into the aircrew because of a medical problem and so taught radio procedures at RAF Cranwell. During his four years with the RAF, one of his students offered him the lead in an amateur production. His success in the role caused him to resolve to become an actor after the war, and so he trained at the Royal Academy of Dramatic Arts, making his first professional appearance on the London stage in 1946. Numerous appearances in London’s West End then followed.
He also appeared in a couple of the most notable Hammer Horror Films including The Curse of the Werewolf and Taste the Blood of Dracula; in the latter he plays a leading role as a Victorian gentleman who betrays Dracula and has to face his revenge.
His first notable television role was as Samuel Pepys in the BBC serial of the same name in 1958. He appeared in the Doctor Who story The Ice Warriors in 1968, playing renegade scientist Elric Penley. In 1970 he was cast in the BBC comedy The Culture Vultures, which saw him play stuffy Professor George Hobbs to Leslie Phillips' laid-back rogue Dr Michael Cunningham. During the production, Phillips was rushed to hospital with an internal haemorrhage and as a result, only five episodes were ever made.
Sallis was cast in a one-off pilot for Comedy Playhouse entitled Last of the Summer Wine as the unobtrusive lover of a quiet life, Norman Clegg. Sallis had already worked with Michael Bates, who played unofficial ring-leader Blamire in the first two series, on stage. The pilot proved popular and the BBC commissioned a series. As of 2008 Sallis is still playing the role of Clegg, and is one of only three cast members remaining from the original Comedy Playhouse pilot, Kathy Staff, who plays Nora Batty, and Jane Freeman who plays Ivy, the cafe owner, being the other two. In 1988 he appeared as Clegg's father in First of the Summer Wine, a prequel to Last Of The Summer Wine set in 1939.
Between 1976 and 1978 he appeared in the children's series The Ghosts of Motley Hall, in which he played Mr Gudgin, an estate agent who did not want to see the eponymous hall fall into the wrong hands.
In 1978 he starred alongside fellow northern comic actor David Roper for the ITV sitcom Leave it to Charlie as Charlie's (Roper) pessimistic boss. The programme lasted for four series, ending in 1980.
Between 1984 and 1990, he alternated with Ian Carmichael as the voice of Rat in the British television series The Wind in the Willows, based on the book by Kenneth Grahame. Alongside him were Michael Hordern as Badger, David Jason as Toad and Richard Pearson as Mole. The series was animated in stop motion, prefiguring his work with Aardman Animations.
Sallis achieved great success when, in 1989 he voiced Wallace, the eccentric inventor in A Grand Day Out. The made-for-television film won a BAFTA award and was followed by the Oscar-winning films The Wrong Trousers in 1993 and A Close Shave in 1995. Sallis has returned to voice Wallace in several more films and productions, including the Oscar-winning 2005 motion picture The Curse of the Were-Rabbit.
Sallis suffers from macular degeneration and in 2005 recorded an appeal on BBC Radio 4 on behalf of the Macular Degeneration Society.