Gosford Park (15)

Shooting party on the Altman estate

Robert Altman, returning to the multi-character drama of which he has been a brilliant and erratic master, is on cracking form in Gosford Park. An upstairs-downstairs comedy of manners entwined with a murder mystery, it showcases aspects of his talent – the relaxed, improvisatory movement, the expert directing of an ensemble, the incisive wit – we haven't seen in a long while. You'd have to go back nine or 10 years, to The Player and Short Cuts, to understand why Altman is good; to understand why he's great, you'd need to rewind even further to the Seventies and the vivid satiric canvases of M*A*S*H, Nashville and A Wedding. This new film can bear the comparisons quite handsomely.

Set in an English country estate over a drizzly weekend shoot in November 1932, Gosford Park is something of an adventure for Altman. He has never made a film about England before, let alone one as ambitious as this, yet far from being cramped by the unfamiliar milieu, he seems to have been emboldened by it. The film anatomises a family, a house, a whole society, with a confidence that verges on the swaggering. This is due, in part, to a wonderfully droll screenplay by Julian Fellowes, working from an idea by Altman and producer Bob Balaban; and partly, it's to do with Altman's instinctive handling of a largely English cast that would be called, in another era, "a galaxy of stars". Ironically, for a film about the disparities of class, the acting is marked by a truly democratic co-operation.

Like the house itself, the film conducts an intriguing two-way flow between upstairs and belowstairs. It takes a while to sort out exactly who's who (and where), but eventually you get the hang of it. Starting from the top, Sir William McCordle (Michael Gambon) is the lord of the manor, a great blustering brute with more affection for his pet pug than his wife Sylvia (Kristin Scott Thomas), who, in turn, amuses herself with favoured servants in her boudoir. Staying for the weekend are various friends and relatives, the most august of them, Sylvia's aunt Constance, Countess of Trentham, a lady marinating in the fatty oils of snobbery and pretence (and played, with exquisite hauteur, by Maggie Smith).

She, like certain other guests, lives precariously on the patronage of McCordle, though she still feels entitled to be sniffy about the standard of breakfast – the marmalade, she spots instantly, is "bought", not home-made – and to insult those guests she deems beneath her, such as the composer and matinée idol Ivor Novello (Jeremy Northam). "How do you put up with these people?" his Hollywood producer friend, Morris Weissman (Bob Balaban) asks. "You forget I make my living out of impersonating them," Novello replies, mildly.

The film thrives on this delicate drift of social nuance. Altman takes time to observe the way status among the underlings operates in virtual imitation of the mob upstairs: visiting servants will be addressed, according to the housekeeper Mrs Wilson (Helen Mirren), by the names of their employers, and dinner placements will be dictated by their rank. So the major-domo Jennings (Alan Bates) insists, for example, on meek young Mary (Kelly Macdonald) sitting further up the table by dint of being Constance's maid. Antagonisms are rife down here, too, between Mrs Wilson and the cook (Eileen Atkins), between head housemaid Elsie (Emily Watson) and the new Scots valet Henry (Ryan Phillippe), between the first footman (Richard E Grant) and anyone he thinks he can lord it over. The society in which the upper hand matters to no one doesn't exist.

Shooting for most of the time with two cameras, Altman (with his photographer Andrew Dunn) glides through the house like an eavesdropper, picking up various intimacies and exchanges on the hoof, and daisy-chaining them into a loose sort of plot. This is a place of secrets – sexual, familial and financial – and for the toffs to keep anything under wraps becomes tricky when there is usually at least one servant hovering nearby. Some secrets are deadlier than others, and later in the film, a murder is committed. Yet the deed is made to feel curiously anticlimactic, because Altman has been dropping not entirely serious hints from the start that things might turn a bit Cluedo: the camera noses up to a bottle on a kitchen shelf marked POISON, and lingers pointedly on a table glinting with knives. Great fuss is made of the producer Weissman forever gabbing on the phone to Hollywood about the next movie he's preparing, Charlie Chan in London – a murder mystery, of course. All that's needed now is Colonel Mustard to show up in the library, with the lead pipe; instead, we have the lead weight of Stephen Fry as a police inspector, whose bumbling incompetence nudges the mood awkwardly towards Clouseau-style farce. It's a feeble part, though given the multifarious brilliancies elsewhere, a misjudgment that can be forgiven.

The size of the cast more or less precludes the possibility of a star turn, yet even with relatively little to do, some performers excel. I loved Richard E Grant's snitty footman, flaring condescension down his nostrils, and Emily Watson as Elsie, full of amused insolence, and Kelly Macdonald, touchingly loyal and put-upon. Kristin Scott Thomas is at her most ravishingly patrician, while Tom Hollander and Charles Dance sketch in deft minor roles as a fearful bankrupt and a laconic war hero respectively. Perhaps the revelation is Jeremy Northam as Novello, the one real-life character in the film, who is very affecting in his gentle gallantry towards a scorned wife of one of the guests, and effortlessly suave as he plays romantic songs at the piano in the drawing-room.

In that sequence may even be buried the meaning of Gosford Park, if it has a meaning beyond exposing the casual rapacity of 1930s pre-war aristocrats, and the drudgery on which they were parasites. As Northam sings, his voice carries through the house, and many of the servants stop to listen, enraptured; some sit quietly attentive on the staircase, or sidle nearer to the door of the drawing-room. A couple of them dance. Contrast this reaction with that of the toffs, who look bored by Novello's entertainment, even irritated. The implication seems to be that these cold-fish aristos are too absorbed in their own preservation to respond to the transforming power of music, of art; their sensibilities have ossified.

The point is made explicit over a dinner conversation in which someone asks Novello about the plot of his latest film; he declines to say, on the grounds that "it would spoil it for you". Constance cuts in: "Oh, don't worry. None of us will see it". One hopes that Gosford Park will not be so lightly dismissed.