Straight after – or maybe during – the terrifying murder in the shower in Psycho, one of the twin peaks of London film criticism at the time, C A Lejeune of The Observer (the other peak being Dilys Powell of the Sunday Times), marched out of the preview. I say ‘marched’ rather than ‘walked’ because it was very obviously and deliberately a protest, watched, eyes popping, by the rest of us. Hitchcock had done his brilliant best to produce what is famously one of the scariest moments and most sadistic murders in the history of the cinema. But he had done more. The unpredictable director, the master of suspense, had turned out his biggest surprise by putting what might have seemed the film’s climax near the beginning, saving another surprise, another even more amazing climax, for the very end.

Psycho dogged its two actors, Anthony Perkins and Janet Leigh, for the rest of their professional lives, even though it wasn’t Leigh’s body that was slashed at, but that of a stand-in. Restrained, even at his most extreme, Hitchcock insisted on using black-and-white rather than colour because he didn’t want