Ingmar Bergman’s extraordinary psychological horror film marked the beginning of a particularly fruitful period for the director and its many complex themes – guilt, the psychological struggles of the artist, questions surrounding identity – would inform many of his key films over the next decade or more. It’s proved to be a hugely influential addition to his filmography (Robert Altman’s Images (1972) and 3 Women (1977), Woody Allen’s Love and Death (1975) and Stardust Memories (1980), Jean-Luc Godard’s Weekend (1967), David Lynch’s Mulholland Dr. (2001) and many more are all directly inspired by the film or contain overt references to it) and has been perhaps more analysed and in more excruciating detail than any other film except perhaps Citizen Kane (1941). It’s been hailed in some quarters as the director’s best work.

It begins with one of Bergman’s most arresting opening scenes, a surreal collection of images including burning celluloid, a crucifixion, a monk setting fire to himself in the street, the slaughter of a lamb and a barely glimpsed erect penis (censored from many prints). A boy (an uncredited Jörgen Lindström) wakes in a hospital bed to provide one of the film’s most iconic images as he sits in front a of a large screen showing the faces of two women. These turn out to be Alma (Bibi Andersson), a young nurse caring for the actress Elisabet Vogler (Liv Ullman) who has been admitted to hospital after suffering some sort of breakdown that has left her almost entirely speechless. Alma is missing her son (possibly the boy from the prologue) but is happy enough to accompany Elisabet to a remote cottage by the sea to help her recover. At the cottage, Alma admits that she feels that no-one has ever listened to her before and she finds herself opening up to the mute but receptive Elisabet, telling her about her fiancé, Karl-Henrik and an orgy initiated by her friend Katarina with two young boys and the shame she later felt at having become pregnant and had an abortion. Relations between the women break down when Alma reads a letter that Elisbet is sending that claims that she’s studying Alma. And things start to come to a head when Elisabet’s husband (Gunnar Björnstrand) turns up and mistakes Alma for his wife and identities continue to fracture and dissolve.

All that analysis mentioned earlier has led to a vast array of readings, theories and interpretations swirling around the film, every writer and academic who wanders into its orbit seemingly finding an entirely different was of making sense of it. When critic Peter Cowie said of it “Everything one says about Persona may be contradicted. The opposite will also be true” he was almost certainly over-stating the case for effect, but one can sense the frustration that many have felt in trying to pin down exactly what the film means. It proved a divisive film in 1965 and remains one today, critics still struggling to pin down exactly what it is – psychodrama, horror film (psychologist Daniel Shaw has written about Persona in terms of a vampire film, while other have seen it as a purely psychological horror about the terror of losing your own sense of self), or just self-indulgent rambling. Bergman himself barely helped, saying that he knew what it all meant but that he wasn’t going to tell us, leaving us to come to our own conclusions instead. And he was good to his word, staying silent on the matter even up to his death in 2007.

On a purely superficial level, it’s a gorgeous looking film thanks to the stunning, luminous photography of Sven Nykvist. The famous shots of the two women’s faces obscuring each other’s and later merging into one are not only visually striking but reinforce one of the film’s many interpretations, that’s it’s all about identity, that Alma and Elisabet are either one and the same or that the former is losing her individuality and becoming Alma, at least in the eyes of others. Bergman’s own screenplay flirts with Jungian theories – Persona is the name that Jung gave to his theory of the social face that an individual presents to the world, one which may not always reflect what’s really going on beneath the surface and which exists to protect the individual from the world around them. It’s perhaps no surprise that the play that Elisabet was in when she became mute was Elektra, which leant its name to another of Jung’s ideas, the Electra Complex, the suggestion that a girl is competing with her mother for the affections of her father. It’s all heady stuff and it’s no wonder that opinions have been so divided.

The whole thing revolves around Bergman’s most famous muses, Bibi Andersson and Liv Ullmann (he described the film as a “sonata for two instruments”) playing the two sides of a woman’s damaged psyche and their performances are electrifying. Persona could easily have been a cold and emotionally distant film, but the two actresses ground it in a way that makes the whole experience as affecting as it is experimental. Bergman gets powerful performances from both of them and Andersson’s sexually explicit monologue about the orgy (partly rewritten by the actress and partly cut in the UK and US releases) is so intense and compelling that it earned as much condemnation as it did praise from the critics. Ullmann, making the first of her ten appearances in Berman films, barely speaks throughout, remaining an enigmatic, almost ghostly presence – it’s Alma’s need to fill the awkward silences she leaves behind that leads her to confess more than she perhaps wanted to.

Largely trapped together in a drab cottage in a remote location, the outside world barely impinges on the two (one?) women. Elisabet, wandering around her hospital room catches sight of horrifying footage of Buddhist monk Thích Quảng Đức setting himself alight in Saigon (also seen in the opening montage) which almost seems to shock her out of her reverie. If we’re to take this literally, and not a sign of some wider social malaise affecting the countryside outside the hospital, it dates the action to the summer of 1963. She also finds a famous image of a young Jewish boy being rounded up by with his family by the Nazis in the Warsaw ghetto in 1943, and they’re the only two reference points to the fact that there’s even a world at all beyond the cottage. And then we can’t be sure how much of this is actually happening in the real world or whether it’s all playing out in the mind (nor indeed whose mind it’s playing out in).

Make of it all what you will, but Persona was always one of Bergman’s own favourites: “I think I can say without singing my own praises that Persona and Cries and Whispers are two films in a class by themselves,” he told Marie Nyrerod on the BBC in 2007. “I think that in this case I have been able to stretch the medium to somewhere beyond its normal limits.” It’s certainly his oddest and most experimental film, utterly unique in his filmography. There’s no question that it’s a horror film but it’s a film unique in the genre too. It’s almost impossible to classify, but equally impossible to resist. It’s one of those films seemingly made expressly to reward repeated viewings – the more you watch it, the more meaning you can tease out of it.

You have to admire the chutzpah of Croatian film student Iva Semencic who, in 2002, remade this most singular and personal of films in a condensed 15-minute format. In 2011, Theatre director Hugo Hansén’s adapted it for the stage and it was followed by another version, by Mattias Andersson and Ylva Andersson, in 2016 and there was a television adaptation in 2019.