Elsewhere, Claire's hotelier husband (Kiefer Sutherland) elects to lord it over his future sister-in-law, stressing how important it is that everyone knows he's funded this particular showcase for his hotel and golf complex. The bride's father (John Hurt) will break off from getting tipsy and trying to get into his fellow guests' knickers to deliver a speech that will be shouted down by his ex (Charlotte Rampling), who herself promptly toasts her daughter by insisting - firmly, in the insistent Rampling manner - that she doesn't set all that much stall in marriage anyway. This, we conclude, is what happens when you book Udo Kier, rather than that nice J-Lo, to plan your wedding. It may also be the single best depiction of nuptial chaos - and the pressure we bring about in undertaking the most joyous day of our lives - that this viewer has ever seen.
The bride, for her part, elects to go AWOL during dessert to look up at a solitary red star in the night sky, and we realise that she, too, is struggling to hold it together, sobbing and snoozing when she's meant to be celebrating, and patently unable to be happy at a moment when everyone around her insists she be. The star - the planet Melancholia, which we learn is set on a collision course with Earth - soon turns billiard-ball blue, threatening to snooker us all; the groom will leave at dawn alone, convinced of his new wife's faithlessness, and facing an uncertain future of his own.
We've already been briefed that the end is nigh by Melancholia's bold opening, a ten-minute prologue composed - and that is the word - of wordless premonitions of the planet's final moments. These are painterly, with a hint of Trierish kitsch: Dunst dressed in black, the energy sapping from her fingers, Claire cradling her son while leaving heavy, irreparable footsteps across the green of a 19th hole, Justine in full bridal gear on the bed of a river, like Ophelia after Millais. With the perversity we've come to expect of him, von Trier shoots these with the same hi-def, slow-motion cameras usually deployed on television to showcase an Ian Bell drive or a Serena Williams forehand, and we sense Lars may yet be making sport of the apocalypse. Is it coincidence that these characters only realise the fun and games are over once they're standing on a golf course? Could it be that, where once we went to play golf on the Moon, now a planet made lonely by our solipsism and lack of curiosity has come to play with us?
I don't doubt some viewers will be glad to see the back of this lot. For a start, there are going to be those who'll want to slap Justine about the face and tell her to stop being such a silly cow; that she has a shiny new job in PR, and the possibility of prima noche congress with the dude from True Blood, and that should be plenty for anyone to be going forward with. Yet it's precisely this expectation that seems to have left her in this state, and which explains all the heavy footsteps she and those closest to her come to leave on those otherwise immaculately tended greens and fairways: when you have the weight of the world pressing down on your shoulders, it's understandable you might well long for that world to end.
Von Trier is too often (wrongly) accused of abusing and demeaning actresses, when actually all he's doing is removing them of their usual glamour (a quality which, in the cinema as in the real world, is useful only up to a point) and allowing us to look at them in new and unexpected ways: inveigling an accoutrement-free, unperfumed Nicole Kidman into the hard theatrical graft of Dogville, turning sprightly Björk into a desperate one-hit wonder for Dancer in the Dark, encouraging us never to follow the sullen Gainsbourg into the woodshed again after Antichrist. Dunst, for her part, has evidently done the reading on depression, or experienced it at close-quarters, if not first-hand: she clocks the self-degradation and abnegation, the inability to empathise, to get beyond her own funk. Von Trier picks out her inner stillness, the dying light in her eyes - what the actress's more mainstream ventures have tended to perceive as mere Valley Girl vapidity - and uses it to give shape and gravitational pull to the character's moods. It's easily a career-best.
The supporting parts are trickier, and the source of my few remaining reservations with Melancholia. Von Trier covers a flaw in his writing with his casting, ordering in actors who are waspish fun to be around (who can resist seeing Hurt and Rampling lock acid tongues?) to play characters who are really no more than nasty fuckers, and whose sole purpose is to do the heroine down at every available moment - to further the sense the entire planet is against her. (Chief offender: Stellan Skarsgard's bullish PR tyro, a thin and rather snidely drawn caricature of privilege.) The whole film, indeed, risks becoming entrenched in its heroine's depressive perspective - everybody's out to get me, even the universe - and appears to settle into a rut halfway through as the action retreats to the Sutherland-Gainsbourg residence, and we await the final countdown.
What happens there is that Melancholia instead turns into a truly cosmic downer, shifting from the first half's Dogme-like intimacies to a consideration of something grander and more profound in scope: it may be the work that persuades even von Trier-phobes that this is undoubtedly, now, a big-picture filmmaker, not merely a petty provocateur engaged in the cinematic equivalent of ginger-knocking. Melancholia's sense of scale is such that it bears comparison with this summer's other major Cannes event movie, to which it provides a fascinating counterpoint: Malick's The Tree of Life, the work of a head-in-the-clouds optimist, which treated the planet's origins, and its perpetuation through the family unit, as a thing of enduring, relentless wonder. von Trier, for his part, has lived in this world: here assuming the mantle of that other great Scandinavian sceptic Bergman in wrestling with the earthly and the spiritual, he offers one of his most outré gambits yet, daring to present the end of days as a blessed release.
Melancholia opens in cinemas nationwide on Friday.