He has played Derek "Del Boy" Trotter in the BBC sitcom Only Fools and Horses, Detective Inspector Jack Frost in A Touch of Frost, Granville in Open All Hours and Still Open All Hours, and Pop Larkin in The Darling Buds of May, as well as voicing several cartoon characters, including Mr. Toad in The Wind in the Willows, the BFG in the 1989 film, and the title characters of Danger Mouse and Count Duckula.

Jason's father, Arthur Robert White, was a porter at Billingsgate Fish Market, and his mother, Olwen Jones, was from Merthyr Tydfil, Glamorgan, Wales, and worked as a charwoman.

In 1967, 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),[9] admired his sense of timing.

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.

Jason appeared in variety shows as the supporting act of Dick Emery and his performances caught the attention of Ronnie Barker.

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.

Jason starred in London Weekend Television's Lucky Feller (1975–76), written by Terence Frisby and produced by Humphrey Barclay.

[12] 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.

In the 1980s, Jason developed a working partnership with Cosgrove Hall, and was a voice-over artist for a number of children's television productions.

[13] In 1981, Jason was cast as Del Boy Trotter in the BBC situation comedy Only Fools and Horses, created by John Sullivan.

Del is a wide boy who makes a dishonest living in Peckham, south London, trading in broken, stolen, and counterfeit goods.

In 1999, Jason starred as Captain Frank Beck in BBC's feature-length drama All the King's Men about the Sandringham regiment lost in World War I.

These include Skullion in Porterhouse Blue (for Channel 4), Sidney "Pop" Larkin in the rural idyll The Darling Buds of May (Yorkshire Television/ITV), based on the H. E. Bates novel, which also featured Catherine Zeta-Jones.

Approached by BBC1 controller Danny Cohen in early 2011, he read three scripts and agreed to shoot a pilot for The Royal Bodyguard, which was shown at the Edinburgh Film Festival.

[19][20] Jason lived with his long-term girlfriend, Welsh actress Myfanwy Talog, for 18 years and nursed her through breast cancer until she died in 1995.

[21] On 26 February 2001, Jason became a father at the age of 61 when his girlfriend, 41-year-old Gill Hinchcliffe, gave birth to a girl in Stoke Mandeville Hospital, Aylesbury.