When Regan and Carter are searching through the rubbish tip, a very brief shot is shown of an Evening Standard newspaper headline "Peer's Nanny is Murdered in Belgravia". This is a chance reference to the notorious case of Lord Lucan who disappeared on 7 November 1974 - presumably a few days before the scene was filmed - and has never been seen since then.
Helen Keating (Busty Barmaid in Cafe) previously appeared in the pilot Regan (1974) as Busty Woman in Pub and later appeared in Messenger of the Gods (1978) as Cathy Clayton.
During the time that this episode was being filmed, John Thaw's wife, Sheila Hancock, was awarded the OBE. When John returned to the set the day after he had accompanied Sheila to Buckingham Palace for her award ceremony, during the filming of the scene in Colet Gardens where Regan and Carter are following Sandy Williams' car, the crew held up a clapperboard marked "HRH", rolled out a red carpet and saluted at John. This red-carpet scene is included in the Out-Takes section of the Series 4 DVD set.
Timothy Carlton (Justin) later appeared with Dennis Waterman in The Howling (1989) and Fool's Gold (1989)