The BFI’s categorisation of the film under its Sound and Music heading is justified by the famous central set-piece: the Albert Hall concert, at the climax of which the heroine (Edna Best) foils an attempt at political assassination. But it is also a ‘family plot’, since Best and her husband (Leslie Banks) are fighting to find and rescue their kidnapped daughter; and it is emphatically a ‘Writer’s’ film, the first of the series of five that were scripted for Hitchcock by Charles Bennett, author of the Blackmail play.

Without his help in creating the template for the ‘Hitchcock thriller’ – adroitly, as here, integrating political and personal narratives – cinema history might have worked out differently. The film’s succession of atmospheric London scenes also makes an important contribution to our sense of ‘Hitchcock’s Britain’.

This film is screening as part of The Genius of Hitchcock: Part Two. A full retrospective of Hitchcock’s 52 surviving films is taking place at the IFI from December 2012 to March 2013.

A six-week Evening Course, Shadow of a Genius, will look at the work of directors influenced by Hitchcock and will take place from February 5th to March 12th.