series Diary of a Young Man (1964), which was partly directed by Ken Loach, in addition to small parts in numerous TV series of the 1950s and 1960s. His best-known role was in Dad's Army as the vicar. His first appearance on the show was in the episode "The Armoured Might of Lance Corporal Jones", which was the first episode of series three. He had worked with producers David Croft before on Hugh and I, and Jimmy Perry at the Watford Palace Theatre. He thought he had come to make a one-off appearance and did not realise that he would become a regular fixture of the show. He would go on to appear in half of the 80 episodes and both feature films. In 2021, Williams said of his time working on Dad's Army that "it was the happiest period of my professional life." Coincidentally, while at Hendon County, Williams wrote in his memoir, he had played the lead in the school play of his final year, The Ghost Train, written nearly thirty years earlier by Arnold Ridley, who would also appear in Dad's Army. Williams featured with Tessie O'Shea in the short-lived sitcom As Good Cooks Go (1970). He appeared in an episode of All Gas and Gaiters as one of the vicars choral in episodes broadcast in 1967 and 1971. At the height of his Dad's Army fame, he had a cameo role in Monty Python's Flying Circus (1972), and later appeared as a record producer in the Rutles movie All You Need Is Cash (1978). He appeared in the short-lived television sitcom High & Dry (1987) as a bank clerk, and he made a cameo appearance in 'Minder', playing a tobacconist. He had a recurring role in You Rang, M'Lord?,a later series written by Jimmy Perry and David Croft. Williams played Lord Bishop Charles appearing in 14 out of a total of 26 episodes. He was a guest on This Morning on Thursday 31 July 2008, talking about Dad's Army with fellow cast members Ian Lavender and Bill Pertwee. He also appeared on BBC1's Jonathan Ross Salutes Dad's Army show on Sunday 3 August 2008. With other surviving members of the Dad's Army cast he walked in the 100th Birthday parade for Queen Elizabeth The Queen Mother, because Dad's Army was her favourite programme. He was the author of several plays, including The Playing Fields and Murder