Truffaut had seduced Hitchcock into doing 30 hours of interviews by means of an imploring letter: “Since I have become a director myself, my admiration for you has in no way weakened on the contrary, it has grown stronger and changed in nature.

Because, Hitchcock explains, he lit it from inside with a little lightbulb. As we watch the superbly sinister scene in the 1941 thriller Suspicion in which Cary Grant slowly, but implacably, ascends a spiral staircase towards Joan Fontaine’s bedroom, we may well wonder why the glass of milk he’s carrying looks so ominous and hyperreal. Hitchcock clearly revels in disclosing some of his secrets. Jones has set them free, juxtaposing the audio recordings with relevant scenes from the films. For 50 years, these conversations have existed in book form.

Kent Jones’s engaging new documentary Hitchcock/Truffaut teems with such moments: the 30-year-old tyro French director asking his hero to explain how he made his films, and the 63-year-old responding in detail, often revealing the lubricious impulses behind such masterpieces as Psycho, The Birds and Marnie. Truffaut seduced Hitchcock into doing 30 hours of interviews, which included chats about Kim Novak in Hitchcock’s 1958 film Vertigo.

Alfred hitchcock and francois truffaut