He was born in London, England, his real name being Horace John Waters. His sisters would become well-known comediennes under the name Elsie and Doris Waters. Like them, Jack Warner made his name in music hall and radio, but he became known to cinema audiences as the father of the Huggett family in a series of popular films.
It was in 1950 that Warner first played the role with which he would forever after be associated, that of PC George Dixon in the film, The Blue Lamp. Although the police constable was killed in the film, the character was revived for the long-running BBC television series, Dixon of Dock Green. The series had a prime-time slot on Saturday evenings, and always opened with PC Dixon giving a little soliloquy to the camera, beginning with the words, "Good evening, all".