This 1960s British whodunnit about an analyst found shot dead in his consulting room is an atmospheric psychological thriller that deserves revisiting if only for the superb cast and evocative London locations.

Ben Hur’s Stephen Boyd handsomely leads the charge as Alex Steadman, a TV commentator coming to the aid of the analyst’s daughter (Pamela Franklin), who believes her father was murdered. Among the suspects are Richard Attenborough’s Chelsea art gallery owner, who just wants his art to be recognised; Diane Cilento’s Hampstead typist, who has intimacy issues; and Jack Hawkins’s Surrey barrister, who wants a past misdeed covered up.

Helping Boyd in his sleuthing are Judi Dench (in her movie debut), Nigel Davenport and Freda Jackson. The list of suspects was supposed to have also included Patricia Neal, but her character was cut from the film and the jury is still out as to ‘why’.

The Third Secret does have its shortcomings (the psychological themes would give today’s therapists a field day, you have to suspend your belief over the way Alex carries out his detective work, and the murderer is pretty obvious long before the hysterical climax), but it’s the way the two leads questionable relationship plays out – against a London riverside filmed in moody monochrome – that really grips. The film’s director, Charles Crichton, would go on to make the hit comedy A Fish Called Wanda. Now, can you work out what the third secret is?

Out on DVD through Odeon Entertainent