Filmed all over Greater London including between Isleworth and Richmond (bridge scene), Kew Garden, British Museum, The Old Commonwealth Institute (nice to see the old interior... shameful they destroyed it and replaced it with the Design Museum), Holland Park, Kensington High Street, Piccadilly Circus, V&A Museum, Horniman Museum, Marble Arch, Chislehurst Caves, Tower of London and many more tourist attractions... as the film was commissioned by London Transport that may be the reason for the hunt for clues. Kim Fortune went on to appear in two Bond films 'Moonraker' and 'The Spy Who Loved Me'
Candace Glendenning was born on August 9, 1953 in Islington, London. As an actress, she is best known for playing Marie one of the Royal children in the award winning film Nicholas and Alexandra (1971).
The source novel by Aylmer Hall, "The Tyrant King - A London Adventure" (published by London Transport in 1967) can be seen advertised on some of the London buses.
The three leads all attended the Italia Conti Academy of Theatre Arts.