Yellow Dog (1973)

Top photographer Terence Donovan tried his hand as a film director with this kung-fu thriller which featured unconventional young Japanese agent Kimura (Jirô Tamiya), who is sent to London on a mission for his government to track down Dr Bewsley (John Welsh), a scientist who has discovered a simple process for turning water into fuel.

Kimura meets with hostility from the British Special Branch in the shape of Alexander (Robert Hardy) and Dover (Joseph O’Conor), but the film’s twisting plot becomes increasingly baffling to follow.

Future Survivors star Carolyn Seymour is highly watchable in and out of bed (why didn’t she become a big star?), and the rest of the cast seems to think the whole thing is a huge in-joke:

Kimura
Jirô Tamiya
Alexander
Robert Hardy
Della
Carolyn Seymour
Dover
Joseph O’Conor
Helen
Hilary Tindall
Dr Bewsley
John Welsh
Jenny Alexander
Angela Thorne
Mundt
Esmond Knight
Marceau
Harold Innocent
Della’s Mother
Madge Ryan
Tim
Jonathan Newth
Eric
Keith Drinkel
Della #2
Gay Singleton
Paulie Alexander
Annabel Lord
David Alexander
Rupert Lord
Sir William Renfrew
Geoffrey Lumsden
Miss Henderson
Belinda Carroll
Galloway 
John Bay
Alin
Harvey Hall
Life Photographer
Grahame Mallard
Fisher
Richard Pendrey
Norman
Noel Davis
Hawk Curtis
Jerome Willis
Vicar
Hugh Sullivan
Inspector Morgan
Michael Godfrey
Bertrum
Brian Hall

Director
Terence Donovan