Based loosely on John Buchan’s book, in which the ‘steps’ were real steps leading down to a landing stage.  The opening memory scene and the love interest weren’t present in the book and the spy knifed at the beginning was a man.

Remade in 1959 with Kenneth More – a version Halliwell called ‘slavish’ – and again in 1978 with Robert Powell, which LH referred to as ‘intermittently vigorous’.

Apocryphal-sounding tales surround the making of the film, with Hitchcock allegedly ‘forgetting’ where the handcuff keys were, causing Donat and Carroll to remain bound together for hours on end.

Hitchcock’s cameo appearance occurs early on: as Donat and Carroll run from the theatre he is seen tossing some litter in the background.