He returned to Civvy Street in 1959 and became a solicitors' clerk. However, the lure of satire was still there and he was still in contact with his old friends at Oxford (who had now formed a firm friendship with John Wells) and who were running their own humour magazines called Parsons Pleasure and Mesopotamia. Rushton was asked to contribute cartoons and features and soon became a favourite with the readers. In particular, Rushton had developed a brilliant eye for caricature and his scathing portraits were much in demand. Mesopotamia became wildly popular, selling beyond the hallowed halls of the universities; so much so that Rushton suggested to his colleagues that they continue the magazine once they had all graduated. Around this time, Rushton also had a near death experience after being knocked down by a bus. He therefore decided that life was too short to be wasted in clerking and that he should concentrate on his real passions. He and his friends began looking for a financial backer.
While all this was going on, Rushton continued to submit cartoons and articles to Punch, Tribune and other magazines. Eventually he got a job with the Liberal News where he illustrated a weekly strip called Brimstone Belcher about a ghastly news reporter (a prototype of Lunchtime O'Booze who would later star in Private Eye).
Private Eye went from strength to strength attracting the cream of Britain's cartoonists and satirists including the late, great Peter Cook. Rushton meanwhile was exploring another aspect of his character - his desire to act. He appeared at the Edinburgh Fringe and in a 1961 production of Spike Milligan’s surreal post-nuclear apocalypse farce The Bed-Sitting Room, directed by Richard Ingrams. But it was his impersonation of Prime Minister Harold Macmillan during a cabaret show that led to greater things. He was spotted by Ned Sherrin, then a young BBC producer, and asked to join the cast of a new TV satire series.
The show was That was the Week That Was (aka 'TW3') and it was one of the most popular TV shows of its day. It regularly drew audiences of 13 million plus and made stars of Rushton and his co-stars David Frost, Kenneth Cope, Roy Kinnear and Lance Percival. It also helped launch the writing careers of such people as John Cleese, Roald Dahl, Graham Chapman, Bill Oddie, Peter Cook, Dennis Potter and many more.
Meanwhile, Private Eye continued to cut a swathe through British politics and when Macmillan retired in 1963 following a health scare, Sir Alec Douglas-Home was pushed to the fore using some very dodgy political machinations. Disgusted by this, the Private Eye team put up their own candidate - William Rushton - as a parliamentary opponent for Douglas-Home in the Perthshire and Kinross by-election (his campaign slogan was Death to the Tories!). Rushton polled only 45 votes, having at the last minute advised his supporters to vote Liberal, the Conservative’s only real competition in that seat. Douglas-Home won anyway.