There are some moments in film that are so overwhelming that they are... well, worth making entire films about. Alexandre O Philippe’s new feature documentary 78/52 (premiering at the London Film Festival) takes its title from the 78 setups and 52 cuts used in the scene in which Janet Leigh is stabbed to death in the shower a third of the way into Alfred Hitchcock’s Psycho. The scene lasts less than one minute but took seven days to film.

These were clearly 45 seconds that shook the world. Philippe’s many interviewees (including film directors Peter Bogdanovich and Guillermo Del Toro, and Leigh’s daughter Jamie Lee Curtis) make a very good case that if you want to understand attitudes to sex, mothers and politics in early 1960s America, this is the only place to begin.

Hitchcock’s decision to kill off a major Hollywood star a third of the way through a film in which she is seemingly the lead character was startling enough. It’s the manner of the death – the queasy, voyeuristic intensity of the scene – that still takes you by surprise, however many times you watch it.

Philippe’s interviewees include editors, actors, composers, academics and critics as well as directors. They talk in great detail about the camera set-ups, the translucent shower curtain, the ‘shrieking’ string music by Bernard Herrmann, and the sanitised look of the motel bathroom. There’s an interview with Leigh’s body double, Marli Renfro, who talks in very matter-of-fact way about how she was looked over by Hitchcock and Leigh and then given the job. However, close to 60 years after the film was made, many are still clearly startled by its raw power.