Born in London and educated at Lylph Stanley School, Williams was then apprenticed as a draughtsman. His relationship with his parents - he hated his father and adored his mother - was key to the development of his later character. He joined the army aged 18, part of the Royal Engineers survey section in Bombay, but later he joined Combined Services Entertainment. After the war he had a number of roles in repertory theatre. He was discovered after playing the Dauphin in George Bernard Shaw's St Joan in 1954; but few serious roles lent themselves to his style of delivery.
He had his break in radio comedy with Hancock's Half Hour from 1954 and then Round the Horne, consolidating this with Beyond Our Ken. In Round the Horne, his roles included the eccentric folk singer, Rambling Syd Rumpo (N.B. not "Sid" as previously listed), and as Sandy, of the extremely camp couple, Julian and Sandy (Julian played by Hugh Paddick); notable for their arch double entendres and use of the fairground slang language Polari (not just gay).
He was a regular for many years on the BBC radio panel game, Just a Minute. He expanded then into television and British films, most notably the Carry On... series. Particularly in the theatre he was famous for breaking out of character and talking to the audience. Although he publicly professed to follow a celibate lifestyle, Williams moved in homosexual circles. His friend Joe Orton wrote Loot for him in 1966, playing Inspector Truscott (!). Following his death, the publication of his secret diaries caused some controversy.
Carry On Sergeant (1958), Carry On Nurse (1958), Carry On Teacher (1959), Carry On Constable (1960), Carry On Regardless (1961), Twice Round the Daffodils (1962), Carry On Cruising (1962), Carry On Spying (1964), Carry On Jack (1964), Carry On Cowboy (1965), Carry On Cleo (1965), Carry On...Follow That Camel (1966), Don't Lose Your Head (1966), Carry On Screaming (1966), Carry On Doctor (1967), Carry On Up the Khyber (1968), Carry On Camping (1969), Carry On Again, Doctor (1969), Carry On Loving (1970), Carry On Henry (1971), Carry On at Your Convenience (1971), Carry On Matron (1972), Carry On Abroad (1973), Carry On Dick (1974), Carry On Behind (1975), The Hound of the Baskervilles (1978), Carry On Emmanuelle (1978).
Television International Cabaret, Jackanory, Willo the Wisp, Hancock's Half Hour
Radio Hancock's Half Hour, Beyond Our Ken, Round the Horne, Kenneth Williams Playhouse, Oh Get On with It, Stop Messing About