In 1941 Guyler married Paddy Lennox from the three-sister variety harmony act the Lennox Sisters, and they had two sons, Peter and Christopher.
Guyler was born in Wallasey on the Wirral Peninsula, Cheshire, and brought up on the other side of the River Mersey in Liverpool, Lancashire, where his father was a jeweller. He attended Liverpool College and originally planned a career in the church. In the 1930s he joined the Liverpool Repertory Theatre and performed in numerous productions. During the Second World War he was called up and joined the RAF Police but was later invalided from Service, whereupon he joined Entertainments National Service Association (ENSA) and then (on 4 May 1942) the BBC's Drama and Repertory company in Manchester.
During the war, he became a regular on the immensely popular radio series, It's That Man Again (ITMA), a series built around Comedian Tommy Handley. Guyler claimed that his character 'Frisby Dike' (named after a Liverpool department store bombed in the Blitz) was the first time the real Liverpudlian accent was heard on the radio. He took part in a Royal Command Performance of ITMA for King George VI and Queen Elizabeth in December 1947. Guyler remained with the show until the death of Handley in 1949 when the series ended.
In the 1950s, he played the time-traveller (also known as "the voice") in the British sci-fi radio series Journey Into Space. Guyler then took on the role in the title character of a Scotland Yard detective in the Light Programme series Inspector Scott Investigates, created by John P. Wynn, that ran from 1957 to 1963. During the half hour programme a crime was committed; Scott and his sidekick, Det. Sgt. Bingham (Brian Hayes, brother of Patricia Hayes) interviewed two or three suspects; then, while music played, there was a short intermission for listeners to guess 'whodunit' before the final reveal. In Henry Reed's series of radio dramas about Herbert Reeve's inquiries into the life of Richard Shewin, Guyler played General Gland, soldier-scholar, campanologist and author of war memoirs, most notably in Not a Drum was Heard. During the 1960s and 1970s, when he starred in the satirical radio programme about life in the British civil Service The Men from the Ministry with Richard Murdoch, Guyler played the pompous, self-important Number One in the General Assistance Department, with Murdoch as his diffident but equally incompetent Number Two.
Guyler holds a unique place in theatrical history, having 'acted' in every performance of The Mousetrap since the opening night on 6 October 1952 in Nottingham, via a recorded news bulletin which is still being used during performances of the play at St Martin's Theatre, London.
One of Guyler's first television appearances was as the manager of a TV repair shop in Three Live Wires in 1961, followed closely by his television success as one of Michael Bentine's sidekicks in the inventive and surreal BBC show It's a Square World (1961), but he gained greater recognition on the small screen in his association with Comedian and Writer Eric Sykes. He played the part of Constable ('Corky') Turnbull in Sykes and a... (1960–65) which was later revived as Sykes (1972–79). In 1975, he appeared in the ITV children's show The Laughing Policeman, based on the Charles Penrose song and his character from the series.
He appeared as the Police Inspector in the Beatles' film A Hard Day's Night (1964) and as the art professor in the Gerry & the Pacemakers film Ferry Cross the Mersey (1965).
In between the two series with Eric Sykes, Guyler was also a regular on the sitcom Please Sir! (1968–72), playing the cantankerous school caretaker Norman Potter. Claiming to be an ex-Desert Rat, Potter would often complain to John Alderton, who played the part of schoolteacher Mr Hedges, about class '5C' and their 'dreadful behaviour'.
Other television appearances include those in That's My Boy, a comedy series starring Mollie Sugden and Christopher Blake, and the short-lived political comedy Best of Enemies. He also played a drunken surgeon in the film Carry On Doctor. During the 1980s he did voice-overs in UK adverts for Scotch Video tapes. He was the narrator of the BBC documentary about Fred Dibnah - Fred Dibnah, Steeplejack
Guyler's passion was collecting jazz records and as of 1986, he had about 1,600 78rpm records, collecting records up to about the year 1947. He was also a virtuoso on the "wash board" (both facts courtesy of It's A Funny Business interview). He was also a well known wargamer, and was a founding member of the Society of Ancients, a group of wargamers specialising in the classical era. Very active in the society in its early years, being elected its first President in 1966, Guyler was later made an honorary life President of the society.
Guyler had been a devotee of washboard playing since his school days and appeared in numerous television light entertainment shows performing his washboard novelty act. In 1990, he played the washboard on three tracks of an album by long-time fan Shakin' Stevens. He also played washboard on an episode of the Morecambe and Wise Show.
A long-time resident of Norbury, South London, he retired to Ashgrove, Brisbane, Queensland, Australia in 1993, to be near his younger son Chris, daughter-in-law Judy and his three grandchildren.
He died on 7 October 1999 and his funeral Service was held at St. Mark's Catholic Church, Inala, Queensland, on 13 October. In 1995 Danny Baker and the BBC had made a 10-minute tribute to Guyler, which was used as a part of the eulogy delivered by his son Chris. Guyler was cremated at Mount Gravatt Cemetery and his ashes were placed at Mount Thompson Memorial Gardens in the Brisbane suburb of Holland Park in a family "garden seat" estate.
His wife Paddy died on 6 January 2002 and is buried with her husband.