It was the film that outraged the censors, terrified the public and prompted the Observer's film critic to storm out of a preview screening and resign in disgust. Yet it now transpires that Psycho may have been tragically misunderstood. Its director, Alfred Hitchcock, always intended it as a comedy.

"The content was, I felt, rather amusing and it was a big joke," Hitchcock explains in a new discovered tape from the BBC archives. "I was horrified to find some people took it seriously."

Hitchcock's made his - perhaps slightly tongue-in-cheek – comments on the BBC show Monitor in July 1964, four years after Psycho's release. The interview now features on the audiobook Alfred Hitchcock: In His Own Words.

"[Psycho] was intended to make people scream and yell and so forth," the director adds. "But no more than screaming and yelling on a switchback railway … so you mustn't go too far because you want them to get off the railway giggling with pleasure."

Widely seen as Hichcock's best – and most shocking – picture, Psycho spins the hilarious tale of a thief (Janet Leigh) who checks into a remote motel owned by a henpecked young man who loves his sick mother (Anthony Perkins). The behind-the-scenes story of the making of the film is documented in the drama Hitchcock, starring Anthony Hopkins and Scarlett Johansson, which is released in UK cinemas today.