Blue Jasmine is the latest film from Woody Allen who, at various stages of his career, has been declared on-form, off-form, sliding-from-form, returning-to-form and, for all I know, as I don’t follow these matters closely, wearing form like a carnival hat with tinkling bells, but there is no need to bother with any of that. All you need know is Blue Jasmine is brilliant. It’s brilliantly written, directed and observed; it’s brilliantly watchable, if not mesmerising; and brilliantly performed, particularly by Cate Blanchett, who will knock your socks off, and may knock them off so explosively there is every chance you will never retrieve them again. (They might be knocked off all the way to kingdom come, for example.) This is possibly a return to form, now I think about it, although whether it’s a return to form from having been off-form or not off-form exactly, just sliding from form, and not yet halfway down, I really couldn’t say. So many ‘forms’. Hard to keep track.

Although Woody — yes, we’re on first-name terms; he’s always admired my work — has denied this is a reboot of Streetcar Named Desire, there is just no getting away from the parallels, or the fragile, self-deluded central character, who is our Blanche DuBois. Here, she is Jasmine (Blanchett) and, when we first meet her, she is travelling on a plane. She has the polished sheen of wealth: a Chanel jacket, a designer handbag held importantly in the crook of her arm; Louis Vuitton luggage. But the way she is babbling, unstoppably, to a fellow passenger instantly informs us she is unhinged, struggling to stay afloat, and we soon learn why.

Her husband, Hal (Alec Baldwin; wonderful), who had been supremely rich, has been exposed as a Bernie Madoff-style conman, and she is fleeing New York for San Francisco and the apartment of her sister, Ginger (Sally Hawkins; cheerful as ever). Jasmine must now rebuild her life, although she does not have the skills to do so, having always lived in a pampered bubble. She and Ginger were both adopted, but whereas Jasmine was the perfect, golden one, thereby growing up with a sense of entitlement, Ginger was not and has just got on with it.

Ginger works in a grocery store, has two kids, an ex-husband, Augie (Andrew Dice Clay), and a boyfriend, Chili (Bobby Cannavale), both of whom work in manual trades, and are very Stanley Kowalski, right down to their vests. Jasmine recalls her past life in flashbacks: the beautiful homes; the shopping; the parties she threw; the baubles given to her on her birthday by her husband. She has tried to stand on her own two feet. ‘I was forced,’ she says at one point, ‘to take a job selling shoes on Madison Avenue. So humiliating. Friends I’d had at dinner parties at our apartment came in and I waited on them. Do you have any idea what that is like? Erica Bishop came into the store. She slipped out thinking I hadn’t seen her.’ Pause. Then an anguished cry to no one in particular: ‘I SAW YOU, ERICA!’ In future, I’m going to cry ‘I SAW YOU, ERICA!’ whenever I am in pain. It just gets right to the heart of it somehow.

There are moments of hope. She gets a job with a dentist, but it ends disastrously. She is courted by a diplomat with political ambitions who wants a trophy wife. (Quite lonely, being a trophy wife: I often look around at parties and think: I’m the only trophy wife here!) Two scenes stand out: one where Chili attempts to set up Jasmine with a blind date over lunch, which is both hilarious and horribly sad, and another when Jasmine babysits the kids, takes them to a fast-food restaurant, talks to them highly inappropriately about her stay in a mental institution where she had electric shock treatments, and then concludes: ‘But I’m better now.’

The film may be about many things: the risks involved in being defined by what you have; the limits of reinvention; the dangers of looking the other way if it suits your own ends; the economic crash; not being able to overturn values that make no sense any more, while corrupting others with them. (Ginger is corrupted, albeit temporarily.) But mostly it is about the human psyche, and what happens when you push someone to the brink of what’s bearable, and they tip over it, and mostly it’s about Ms Blanchett, who owns this throughout. She fully inhabits Jasmine: her disintegration, her terror, her guilt, her shame. She acts without vanity — mascara-smeared eyes; sweat-stained underarms — and is able to convey the cornered, terrified animal behind the polished façade. It’s Woody on top form, although whether this is more top form than the last time he was on top form, I couldn’t say.