His impersonation of the Conservative prime minister Harold Macmillan was a highlight of the BBC series, which outraged politicians but was, more significantly, a symbol of the way in which this new generation were truly appalled by the Conservative government of the time.
A cartoonist, humorist and satirist, Rushton - born in London, the son of a publisher and grandson of a Wigan lawyer who was right-hand man to Lord Leverhulme - found a training for his satirical exploits at Shrewsbury School, where his contemporaries included the future editor of Private Eye Richard Ingrams, the author Christopher Booker and the journalist Paul Foot. There, they parodied the school magazine, the Salopian, with their own publication, the Wallopian, exchanging stories of the 1st XI's latest successes for a more irreverent view of the public school and its masters. It included Rushton's cartoons, which were to become a constant part of his output throughout his working life.
It was also at Shrewsbury that Rushton developed his acting talents, most notably playing the old man Lord Loam in The Admirable Crichton. "The audience wondered which elderly member of staff had been dragooned into playing Loam," he later recalled.
Unlike those Oxbridge graduates such as Peter Cook who were largely responsible for bringing the satire boom to Britain, with its roots in the stage show Beyond the Fringe, and in Private Eye and the Establishment Club, Rushton did not attend university. He topped up his extra-curricular experiences at Shrewsbury by doing National Service in the Army, which he described as "one of the funniest institutions on Earth . . . a sort of microcosm of the world", adding: "It's split almost perfectly into our class system. Through serving in the ranks, I discovered the basic native wit of my fellow man - whom, basically, to tell the truth, I'd never met before."
Subsequently finding himself back in civvy street but out of work, he was employed as a clerk in a solicitor's office until, with Richard Ingrams and Christopher Booker, the idea of Private Eye was germinated in a Chelsea pub. The magazine, launched in 1961, proved a huge success and it was Rushton's cartoons that helped to establish its distinctive identity.
In the same year, he made his professional stage debut in Spike Milligan's nuclear attack satire The Bed-Sitting Room at the Marlowe Theatre, Canterbury. This led to an invitation to join the team that was to launch upon the nation That Was the Week That Was (1962-63) on BBC television. The timing was perfect for the new Saturday-night show produced by Ned Sherrin, with Beyond the Fringe playing to packed houses in London and the Establishment Club satirists creating new targets for their uncompromising wit.
The previously unknown David Frost was chosen to present TW3, as it became known, and his regular cohorts included Rushton, Roy Kinnear, Kenneth Cope, Lance Percival, John Wells, John Bird, Eleanor Bron and Roy Hudd, while Millicent Martin performed songs giving topical events a similarly irreverent perspective. The programme provided an outlet for writers such as Keith Waterhouse, Willis Hall, Malcolm Bradbury, John Cleese, David Nobbs, Jack Rosenthal and Dennis Potter. It quickly caught the imagination of the viewing public, with audiences of up to 13 million and, one week, as many as 443 angry phone calls. As well as his Harold Macmillan impersonation, Rushton was remembered affectionately for his Colonel Buffie Cohen characterisation but also had to endure complaints about his scruffiness on the show.
The sequel, Not So Much a Programme, More a Way of Life (1964-65), broadcast on Friday, Saturday and Sunday nights, failed to find the same formula for success and Rushton left, disenchanted, after only a few weeks. Although controversial, the programme lacked the biting humour of the original.
In the meantime, egged on by his Private Eye colleagues, Rushton stood against Alec Douglas-Home in the 1963 Kinross by-election but won only 45 votes. Although a lifelong Labour Party supporter, he later admitted that he was not "very good with organisations". Those who knew him reflected that he used humour as a smokescreen to avoid discussing serious issues in a pretentious way. "My basic defence is Blitz humour," he once said.
Another failure was Rushton's short run as host, with the actress Jill Browne, of the television show The New Stars and Garters (1965), a retitled series of the traditional pub entertainment variety show Stars and Garters. In TW3 vein, Rushton found his talents used more successfully in Peter Cook and Dudley Moore's legendary series Not Only . . . But Also (1965- 66). Satirical but of lesser stature was his appearance as Plautus in the Frankie Howerd series Up Pompeii! (1970), scripted by the writer of the Carry On film series, Talbot Rothwell, and starring Howerd as a Roman slave in ancient Pompeii. The painful puns and double entendre lacked the subtlety and wit of the TW3 crowd.
Rushton's theatrical career continued on an occasional basis with Gulliver's Travels (Mermaid Theatre, 1971, 1979) and Eric Idle's Pass the Butler (Globe Theatre, 1982). Throughout the Sixties and Seventies, he also took cameo roles in the films Nothing But the Best (1964), Those Magnificent Men in Their Flying Machines (1965), Monte Carlo or Bust (1969), The Bliss of Mrs Blossom (1968), Flight of the Doves (1971) and Adventures of a Private Eye (1977).
In 1974, Rushton turned up in a dramatic role on television as Major Trumpington in the BBC series Colditz. Complete with red beard, kilt and woolly hat, the character was one of three commandos captured on the French coast and taken to the infamous castle. Rushton's own series Rushton's Illustrated (1980) failed to make a great impression and most of his subsequent television appearances were as guest in quiz and game shows such as Celebrity Squares (1985-89).
His quickfire wit found a more appropriate outlet through 27 series of the BBC Radio 4 show I'm Sorry I Haven't a Clue, starting with its first broadcast in 1967. He also starred as the overgrown schoolboy Nigel Molesworth in the four-part BBC radio series Molesworth (1987) and was in demand as a storyteller for Jackanory on television. Earlier this year, he toured with Barry Cryer in the stage show Two Old Farts in the Night.
To the end, Rushton continued to provide cartoons to a publications ranging from the Daily Telegraph to the Literary Review and Private Eye (for a long time he contributed a contents page illustration to the Independent Magazine), as well as illustrating for the Channel Four television series Rory Bremner . . . Who Else? (1993-96). His work as a cartoonist has been displayed at both the Victoria & Albert Museum and the National Portrait Gallery.
Rushton was also the author of humorous books such as William Rushton's Dirty Book (1964), The Filth Amendment (1981) and Willie Rushton's Great Moments of History (1985) and the spoofs The Day of the Grocer (1971), Superpig (1976) and Spy Thatcher (1987), as well as Every Cat in the Book (1993).
William George Rushton, cartoonist, writer, actor and broadcaster: born London 18 August 1937; married 1968 Arlene Dorgan (one son); died London 11 December 1996.