Given a welcome spruce-up for its 70th anniversary, Hitchcock’s prescient conspiracy caper still has a spring in its step and an upward turn to its determinedly stiff upper lip.

Wartime favourite Margaret Lockwood plays Iris, a lively lass (but a reluctant fiancée) who is one of several mostly English travellers stuck in a hotel somewhere in the mountains of central Europe.

Before finally boarding the train home, Iris receives a bump to the head and is taken under the wing of kindly old dear Miss Froy (Whitty). A few hours later, Iris awakens to find her companion gone.

Confusingly, nobody can recall Miss Froy ever being on board. A passing brain surgeon (Paul Lukas) explains it away as mild head trauma but Iris is convinced that it’s all part of some strange plot.

Her only ally is Gilbert (Redgrave), the irritating yet vaguely charming fellow from back at the hotel. But the determined pair soon find that this is as dangerous a puzzle as they will ever have to solve.

The Lady Vanishes marks one of the rare occasions that the performances are more memorable than Hitchcock’s staging.

Naturally, nobody builds suspense like ‘The Master’, but the appealing team of Lockwood and Redgrave receves sterling back-up from twinkly Dame May and Cecil Parker as the spineless adulterer who’d rather put an old woman in peril than see his reputation ruined.

But it’s Basil Radford and Naunton Wayne who fold the acting honours into their over-starched pockets as Charters and Caldicott, a pair of thoroughly English boobs whose sole concern is that this infernal nonsense is keeping them from the cricket in Manchester.

The film’s age only becomes apparent through its model sets, but the back-projection techniques and some of Hitchcock’s visual tricks were no less sophisticated than the anything seen in the music videos of the 70s and early 80s.

Coupled with a Launder-and-Gilliat script fizzling with British bluster and moments of pure cheek, this is Hitchcock at his most playful.

But, made before World War II broke out, the film was also a gentle propaganda piece, warning cinema-goers of the encroaching Nazi menace.

It’s all jolly well enjoying yourselves in those picture houses and telling everyone else about it, but loose lips sink ships, what?

Elliott Noble