Early years
Jason started his television career in the made-for-TV film Mother Goose (1965). He played Bert Bradshaw in Crossroads in 1966. In the following year, he played spoof super-hero Captain Fantastic, among other roles, in the children's comedy series Do Not Adjust Your Set (Rediffusion London/ITV) with Eric Idle, Terry Jones, Denise Coffey, and Michael Palin. Humphrey Barclay, who recruited Jason to appear in Do Not Adjust Your Set (partly to counter the more highbrow style of Idle, Jones, and Palin), admired his sense of timing. The programme ended in 1969, and the character then appeared for a time in the Thames Television children's programme Magpie. Jason appeared in the BBC comedy series Hugh and I in 1967, which starred Hugh Lloyd and Terry Scott as two friends who lived together in South London. He appeared in the Randall and Hopkirk (Deceased) episode "That's How Murder Snowballs" (1969) as Abel, a framed performer in a major London theatre.
In 1968, Jason was initially cast in the role of Lance Corporal Jones in the Jimmy Perry and David Croft BBC comedy Dad's Army. Croft had been very impressed with Jason and believed that he had the talent to play a man much older than his real age (though he was only 28 at the time) but BBC executive Bill Cotton overruled him, casting Clive Dunn because he was better known. According to Jason, "I was cast at 12 o'clock and sacked by three." Jason also missed out on the starring role of Frank Spencer in Some Mothers Do 'Ave 'Em in 1973 because BBC executives at the time believed that he lacked "star quality".
In the 1970s, he also acted in radio comedies, including the weekly topical satire Week Ending (in which he regularly played such figures as then UK Foreign Secretary David Owen) and The Hitchhiker's Guide to the Galaxy (as the "B Ark Captain" in the sixth episode). Jason also appeared in The Next Programme Follows Almost Immediately and made appearances on panel games such as The Impressionists as well as his own series, The Jason Explanation. In the early 1970s, he appeared in Mostly Monkhouse.
Jason appeared on stage in the West End in the farce No Sex Please, We're British playing Brian Runnicles for 18 months in 1973. He also starred with Valerie Leon in a stage comedy, Darling Mr London, which toured in 1975.
Jason appeared in variety shows as the supporting act of Dick Emery and his performances caught the attention of Ronnie Barker. Jason was recruited to appear in Hark at Barker (LWT, 1969), starring opposite Barker's Lord Rustless, as Dithers, the 100-year old gardener. There was also a sequel, His Lordship Entertains (1972), for the BBC. Jason played idealistic employee Granville in the first programme of the comedy anthology Seven of One (1973), called Open All Hours (BBC) and starring Barker as the curmudgeonly proprietor of a corner shop.
Four series of Open All Hours were made from 1976 to 1985. He featured in Barker's Porridge (BBC), a prison comedy, as the elderly Blanco in three episodes. Jason also appeared with Barker in various disguises in The Two Ronnies, including providing the "raspberry" sound effect for The Phantom Raspberry Blower of Old London Town.
Jason starred in London Weekend Television's Lucky Feller (1975–76), written by Terence Frisby and produced by Humphrey Barclay. About two brothers in south-east London, the series was in many ways a forerunner to Only Fools and Horses. He played the lead role of Peter Barnes in the ATV sitcom A Sharp Intake of Breath (1977–81), alongside Alun Armstrong and Richard Wilson. In 1979, he appeared as Buttons in the pantomime Cinderella at Newcastle's Theatre Royal, starring Leah Bell and Bobby Thompson, produced by Michael Grayson and directed by John Blackmore.
