Alfred Hitchcock's 1960 low-budget shocker Psycho slashed the link with Hollywood's golden past as viciously and relentlessly as the shower skewering of Janet Leigh's Marion Crane in the most infamous scene in movie history.
Hitchcock made better and more ambitious movies - Vertigo was recently voted the greatest movie of all time - while The 39 Steps, Rebecca, Notorious, Strangers on a Train and Rear Window are more typical of his style and more cherished by his fans.
But it is impossible to overestimate the impact of Psycho, which brought to Hollywood new levels of menace, violence and sexuality (albeit suggested rather than shown in that masterful Hitchcockian way) that tapped the dark undercurrents that had been welling in Eisenhower-era America and would be unleashed in the following decade. Movies were never the same again.
Unfortunately, none of this emerges from Hitchcock, Sacha Gervasi's lively, amusing and wonderfully well-acted account of the making of Psycho, which nonetheless buries its fascinating subject under a cloak of conventional Hollywood melodrama, half-baked pop psychology and, for those who know the real story, flat-out bunkum.
Instead of sticking to the intriguing story of how the 60-year-old director defied his Hollywood masters and reinvented himself artistically by shucking off the machinery of big-budget movie-making (he had just come off the glamorous Cary Grant spy thriller North By Northwest), Gervasi shifts the focus to his relationship with his wife and long-time collaborator Alma Reville (Helen Mirren).
I have no problem with the low-key Alma finally getting her due as his Hitch's right-hand woman. But Gervasi goes too far in the other direction, having Alma suggest they kill off Marion a third of the way in (that was in Robert Bloch's novel), rewriting the screenplay (the late Joseph Stefano might have something to say about that), marching on set to direct scenes when Hitchcock was ill (she never went to the Psycho set) and indulging in a flirtatious dalliance with the writer Whitfield Cook (an old story dredged up from a decade past).
Rather that centering on his determination to break new ground artistically and match the new wave of erotic thrillers coming out of France, we get Hitchcock (Anthony Hopkins) going off the rails, suspecting his wife of having an affair with the charming skirt- chaser Cook (Danny Huston) and identifying with the real-life serial killer who inspired Bloch's book, the appalling Ed Gein.
This emphasis makes for a heady psychological brew and reminds us that Hitch was a very peculiar, perverse man, as we know from the numerous biographies. But to highlight all of the director's manias and inadequacies at the expense of showing one of the masters of cinema at the top of his game, an artist who controlled every aspect of the filmmaking process, is ludicrous.
Scenes such as Hitch grabbing the knife while shooting the shower scene and channelling all his murderous anger on to a shocked Leigh (Scarlett Johansson) and begging Alma to use her editing skills to save his movie that had turned out to be a lifeless disaster are dramatic, certainly, but an insult to movie history's greatest control freak.
While I don't recognise "the Master of Suspense" from Gervasi's movie and the improbably sassy, sexy Alma seems to have been dropped in not from real life but another movie, it's great fun watching Hopkins and Mirren putting their spin on a couple who'd worked closely together since the days of silent cinema.
Hopkins doesn't really look like the famously rotund grocer's son but he nails that appealing mix of faux gentility, intelligence, mordant humour, sadness and self-pity to give Hitch a richness and a depth the overall film lacks; while Mirren, despite being way too beautiful to play the plain Alma, does give her the sense of authority and cleverness we know she possessed.
Hitchcock is at its best when Gervasi plunges into the filmmaking process - Hitch finding Bloch's book and having it removed from book stores to hide the secret, locking horns with Paramount bosses over budgets and bad taste, facing off with the censors and using all of his showbiz nous and chutzpah to turn his "grubby" little B-picture into a phenomenon.
But don't mistake Hitchcock for an accurate account of the creator of arguably the greatest body of work in film. Go to the biographies, the documentaries, the recently released Blu-Ray collection and look at the movies. That's the true window into the soul of Alfred Hitchcock.