It had been a long time coming, but the BBC finally had some good news last week when Noel Edmonds, one of the architects of dumb television, resigned in a greedy huff. Yet it’s the accumulation of such moments that makes Hitchcock’s work so unique and so instantly identifiable. It’s why calling his films “well-directed”, as British critics used to do, is an insult to a great artist. Who, after all, would dare to call a novel by Kafka “well-written”? Or a painting by Picasso “well-painted”?David Thomson writes about Robert Walker in Film Studies, opposite. Whereupon, as one does, a fellow passenger asks him for a light.

Since Bruno, now abruptly alert, realises how dangerous it would be to expose the lighter, he continues to clutch it in one hand while, with the other, awkwardly fishing a book of matches from his jacket pocket. The fellow passenger meanwhile stares at him as though he’s faintly mad.It’s a nothing moment, almost imperceptible, as I say The film doesn’t need it It would be just (or nearly) as good without it. He’s on the train again, mighty pleased with himself, so much so that he nonchalantly uses the stolen object, on which is embossed two small but distinctive criss-crossing racquets, to light one of his own cigarettes. (A celebrated anecdote, tirelessly repeated by the director but seemingly not apocryphal, tells of a chubby little Hitch locked up for five minutes by his father, as a joke, inside a police cell.) For anyone, then, seeing the film again, it’s no longer the familiar set-pieces which linger longest in the mind – the fun-fair murder, the wildly careening merry-go-round – but a few jarring moments that, even when almost imperceptible, instill that old Hitchcockian unease.Consider the scene, precisely, in which Bruno travels back to the funfair to plant Guy’s lighter. Beyond its quality as an entertainment (and Hitchcock’s films remain among the most entertaining ever made), there is to Strangers on a Train a formal sophistication unmatched by anything in the current mainstream cinema.It may be “only” a thriller but, like all his best work, it taps the unvoiced anxieties that lurk within all of us; for just as Chaplin never forgot his childhood poverty, so Hitchcock never forgot his childhood fears. With Psycho it’s the circle, Vertigo the spiral, North by Northwest the diagonal line and Strangers on a Train the criss-cross. Everything criss- crosses in this film: the two pairs of legs, of course, which are responsible for setting the whole plot in motion; the railway tracks; the swapped crimes (one blithely carried out by Bruno, the other naturally not by Guy, who has imagined, while airily half-entertaining the idea in Bruno’s compartment, that he is only humouring a harmless simpleton); and, above all, the marvellous sequence in which Hitchcock cross-cuts between Guy on the tennis court and Bruno, about to “plant” Guy’s cigarette lighter at the scene of his own crime, desperately struggling to retrieve it from under a sewer grating into which it’s fallen.

It’s one of the key concepts of Hitchcockian exegesis, and variations can be found in film after film (I Confess, The Wrong Man, North by Northwest, Psycho and so on) This is how, and why, the so-called auteur theory works. Even in the case of a literary adaptation, a truly personal film- maker already contrives to assert his identity and individuality in the choice of material.Another commonplace of Hitchcock criticism is the notion that the principal narrative elements of each of his films are, consciously or not, organised around a latent motif, one usually based on a simple geometrical form. It is, in effect, a perfect example of the “transference of guilt”, by which a protagonist finds himself forced both to assume and to expiate another’s crime. The someone, as it happens, was Patricia Highsmith, on whose novel the film is based. (Raymond Chandler was one of the scenarists.) But if Hitchcock chose to adapt it to the screen, it was surely because he knew that its premise was quintessentially Hitchcockian. Which is when Bruno declares his immaculately manicured hand. Why don’t they exchange murders? Each does away with the other’s bete noire; neither, therefore, will have any detectable motive; each gets what he wants and neither ends up in the electric chair.The basic idea is breathtakingly simple, except that someone had to think of it.