In 1976 CID's DS Alan Bruton and DC Len Clayton were introduced to inject new life into the 21-year-old series (this was also the reason Dixon's opening/closing monologues were delivered in plainclothes from his office, rather than the previously-used London backdrop). It was hoped this would 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.
Acknowledging George Dixon's advancing age at the time of the last series, it is 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. (This was not, however, a job Warner's character had been specifically identified as undertaking previously.)
When Jack Warner died in 1981, aged 85, his coffin was borne by officers from Paddington Green police station, where series creator Ted Willis had done much of his initial research for the show in 1955.
The trivia item below may give away important plot points.
Andy Crawford features in all but the final run 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.