Only 33 of the series' 432 episodes survive: 12 from the monochrome era (1955-1968) and 21 from the colour run (1969-1976). The others were wiped by the BBC. Seasons Three, Four, Six, Eight, Ten, Twelve, Sixteen and Nineteen are missing entirely; conversely the final, 22nd season is the only one to survive completely. Off-air recorded soundtracks also exist for Double Jeopardy (1968), The Trojan Horse (1968), Nightmare Hours (1971) and There's Your Story, There's My Story - And There's the Truth (1974), which were recovered in 2015.
Jack Warner was already 60 when the series began, past the age (55) at which a policeman would retire. George Dixon is thought to be - loosely - aged in his 50s throughout the series. Acknowledging his visibly advancing age by the time of the concluding run (by which time Warner was in his early 80s), it's said that his service has been specially extended in order to train Police Constable Harry Dunne as his replacement in the Dock Green Collator's office - not a rôle Dixon had been identified as undertaking previously.
In 1976 Criminal Investigation Department's Detective Sergeant Alan Bruton and Detective Constable Len Clayton were introduced, to inject new life into the twenty-one-year-old series (this was also the reason Dixon's opening and closing monologues, planned to be eliminated until Warner intervened, were delivered in plain-clothes from his office rather than the previously-used London backdrop). It was thought this could broker a Dixonless series called simply "Dock Green". The idea was floated during production of what would become the final run, to decidedly unenthusiastic response.
The series theme tune by Jeff Darnell was released in 1958 on the Oriole Records label as "An Ordinary Copper", performed and with lyrics by Jack Warner, with Tommy Reilly on harmonica. The disc number is CB 1426. Darnell and Warner had long performed together as a music hall double act.
Andy Crawford features in all but the final season of the show. He is said to have transferred to A10 (the Met's anti-corruption branch) at the beginning of the 22nd season. Series producer Joe Waters did some preliminary work on a proposed Soho-based spin-off for the character (to be called "West End Central") which ultimately came to nothing.