Just 33 of the series' 432 episodes are known to 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 held in full. 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 PC 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 Det. Sgt. Alan Bruton and Det. Con. Len Clayton were introduced, to inject new life into the 21-year-old show - also the reason George's opening and closing monologues (planned to be dropped until Warner intervened) were delivered in plain-clothes from his office rather than the usual London backdrop. It was thought this may help broker a Dixonless series called simply "Dock Green"; the idea being floated during the final run's production to mixed response. Director Michael E. Briant recalled that he was certainly under the impression that the series would return the following year, following Warner's assumed retirement from his rôle.
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, where he's transferred to the Met's anti-corruption branch, A10. 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.