The best picture winner can only be Alfonso Cuarón’s glorious and very personal movie Roma, co-produced with Nicolás Celis and Gabriela Rodriguez. This jewel is inspired by his own upbringing in early 1970s Mexico City, and his family’s complex relationship with their beloved live-in maid. The film’s engagement with race, culture and class together with its staggeringly choreographed setpieces and sublimely inspired incidental detail all come together with Yalitza Aparicio’s wonderful lead performance to weave a spell.

Part of it is Cuarón’s miraculously unforced narrative flow. So many movies look like they have come out of screenplay-seminar thinking: three acts, show-don’t-tell, character arc, obstacles surmounted, life-lessons learned. By contrast, Roma just spills out unhurriedly on to the screen, moving this way and that, like the water being patiently sploshed by the maid Cleo on to the tiled driveway under the film’s opening credits. It has an inspired fluency, uncoerced, unmanaged, full of digressive ease.

In its way, this is a very novelistic film, with the accretion of detail you might expect from a Bildungsroman. The experiences of Aparicio’s maidservant character Cleo do not take her on anything as explicit as a personal “journey”, but something more mysterious and internalised. We see what Cleo sees, we wonder what and how she feels, we build up our investment of sympathy with her, and it all leads to a heartrending payoff. I have still never seen the climactic scene clearly – having been semi-blinded by tears each time.

Cleo is a young woman of Mesoamerican heritage working as a live-in maid for a beleaguered upper-middle-class family in Mexico City. Cleo’s personal life is beginning to disintegrate alongside that of her employer, Sofía (Marina De Tavira), mother to four lively kids — though it’s Cleo who has to do the childcare heavy lifting. Cuarón shows, through a hundred little touches, that though their handsomely appointed household is superficially comfortable, the family is, in Tolstoy’s words, unhappy in its own way. The father, Antonio (Fernando Grediaga), is increasingly late home, parks his car with fanatical precision in the driveway in a way that hints at dysfunction and repressed anxiety. Soon he is away on what Sofia tells the children is a business trip but tearfully asks them to write letters to their papa begging him to come home. Meanwhile, Cleo forms a relationship with a dodgy martial-arts enthusiast, Fermín (Jorge Antonio Guerrero) who is less than supportive when she explains she has missed her period.

There are some amazing and almost dreamlike scenes in the film, left-field adventures which never look extraneous, but like the things that can happen in real, rather than surreal life: a family trip to friends in the country featuring a hair-raising shooting trip, a New Year’s party which culminates in a forest fire and one guest singing an earnest Scandinavian hymn. Fermín demonstrates his martial arts moves to Cleo in a postcoital display of self-love. Cleo later tracks him down to a weird outdoor paramilitary motivational meeting outside town. Cuarón’s finds these moments with serendipitous inspiration, and his Mexico City streetscapes are sensational, thrillingly alive, worthy of Scorsese, especially in the evocation of the Corpus Christi massacre, when around 120 people were killed by the military during a student demonstration, and which here has a sensational personal significance. Cuarón’s own superb monochrome cinematography reminded me of Michael Chapman’s work on Raging Bull.

It is all heading to Cleo’s own terrifying moment of truth, to the revelation about her love for the four children under her care: what she has done for them, what she has sacrificed for them, and what life has given and taken from her. There is a quiet grandeur in these scenes. With quiet dignity, she is the moral equal of everyone she meets: the children she cares for, the woman who employs her, the doctor who treats her. That is her victory. What a wonderful movie it is.