As mouths go, it must be one of the most fabled of the century past. The lips, as widely parted as they could be, suggest the contours of a distended heart. There is an upper gallery of teeth, slightly imperfect, and glazed by spittle mingling with the crystal darts and droplets of a powerful jet of water issuing relentlessly from above the face. A mottled tongue is barricaded in by the lower gallery of teeth, almost as pinned by them to the floor of the mouth. It’s a sensual, importunate mouth, the sort that might belong to a popular diva giving new life to a favourite old tune from Sacha Distel or Gene Kelly; but instinctively we know –the mouth is so legendary – that this is not the case. Those are no raindrops falling on her head. And she’s not singin’, whether in the rain or anywhere else. She’s screaming in the shower of Bates Motel, screaming for dear life as the presiding matriarch of that decaying Gothic hostelry (or so we’re led to believe) remorselessly bears down upon her with an elongated knife, and to a very different, lethally staccato tune.

The real owner of the mouth, of course, is Janet Leigh, playing the part of the set-upon blonde in Alfred Hitchcock’s Psycho (1963). The actress lives on to this day (though legend has it that since the film she’s never been able to take another shower); and the famous image of her mouth is revived once more to adorn the jacket, back and front, of an exhilarating new book, The Hitchcock Murders (Faber), by the Australian expatriate writer, Peter Conrad.