Kudos to his collaborators, first of all. Frank Launder and Sidney Gilliat's screenplay is sharper than anything written for Hitchcock's other British films (or his American films, come to that – except possibly for North by Northwest) and you could make a strong case for regarding it as a Launder and Gilliat film rather than a Hitchcock one, if authorship has to be decided. That sometimes endearing indifference to nuances of dialogue and characterisation that marks even some of Hitchcock's best films is nowhere to be found here: the edgy banter between Michael Redgrave and Margaret Lockwood really sparkles.
And then, of course, there are Charters (Basil Radford) and Caldicott (Naunton Wayne), two of the finest creations in British cinema: a blissful satire on stiff-upper-lip Englishness, but also (at a time when the country was gearing itself up for war) a celebration of it. In one scene, Charters gets shot in the hand by an enemy gunman, bringing home to him, for the first time, the gravity of the danger the Brits are facing. "You were right," he says to Gilbert calmly, while dabbing at the bloody wound with a handkerchief. It's a moment that never fails to elicit gasps of admiration as well as disbelieving laughter from the audience.
Ethel Lina White's original novel, The Wheel Spins, is a leaden affair. Hitch seems to have briefed his writers, as usual, to read it through once for the story and then forget about it. Launder and Gilliat relocate the action to the imaginary middle-European country of Mandrika, and turn the whole of the first half hour into a low-key but brilliant bedroom farce. Once the characters are all aboard the train and homeward bound, the mystery kicks in and the film becomes more "Hitchcockian".
But it always remains a comedy as much as a thriller, and I suppose it's my own love of British film comedy that gives it a special place in my heart. Redgrave's impersonation of Will Hay aboard the train reminds us that Hay was one of the biggest British stars at the time and, looking forward 20 years or so, the cinematic world the film foreshadows belongs more to Terry-Thomas and Ian Carmichael than Scottie Ferguson or Norman Bates.