Train thrillers were all the rage in the 1930s. Agatha Christie published Murder on the Orient Express in 1934, while Ethel Lina White's play, The Wheel Spins, had opened in the West End two years later. The latter's screen adaptation was written by Frank Launder and Sidney Gilliatt, who were no strangers to trainbound mysteries themselves, having penned Seven Sinners in 1936. Indeed, the two most memorable characters in this enduringly enjoyable Hitchcock classic, Charters and Caldicott, were inspired by Gordon Harker's golf nut in Rome Express and the voluble corset salesman that Robert Donat encountered en route to Scotland in Hitch's The 39 Steps.
As he would later prove with Lifeboat (1944), Rope (1948) and Rear Window (1954), Hitchcock was the master of confined spaces and he makes splendid use of the train's compartments and corridors to emphasise the audacious ingenuity of Dr Hertz's kidnap plot.
However, it's the dialogue and characterisation that make The Lady Vanishes so mischievously gratifying. Countless lines crackle with wit and insinuation, whether it's adulterous politician Eric Todhunter (Parker) trying to sustain a modicum of propriety with his mistress Margaret (Travers) or Gilbert discussing his parentage and his relationship with the German woman who pays his rent.
But much of the humour centres on Charters and Caldicott, who were brilliantly played (as they would be in several subsequent features) by Basil Radford and Naunton Wayne, neither of whom were particularly known for their comic prowess. However, they don't just provide light relief. They also confound Hitler's view of the British as Woosteresque buffoons and someone at the Reich's Chancellory should have noted how they not only did their bit in the shoot out, but also enabled Mrs Froy to slip away undetected and helped drive the train to safety.
Released to coincide with the Munich Crisis, the film proved a major success on both sides of the Atlantic and was key in securing Hitchcock an invitation to work in Hollywood.