Robert Altman's country house murder mystery is a veritable who's who of veteran British acting talent.

Who's that lurking behind the drinks decanter - it's none other than Michael Gambon. And that's Derek Jacobi pressing a blouse belonging to - guess who? - Dame Maggie Smith.

That Altman can successfully marshall this enormous ensemble cast is achievement enough...but he also manages to dot the characters around a neat Agatha Christie-style plot.

We join the house party organised by Sir William McCordle (Gambon) and his frosty snob of a wife Lady Sylvia (Kristin Scott Thomas) as the guests arrive.

There's her aunt - impoverished aristo Constance (Smith), deaf Lord Stockbridge (Charles Dance), scheming Freddie Nesbitt (James Wilby) and skint ex-officer Anthony Meredith (Tom Hollander).

These dusty relics of the class system are joined by new money - British matinee idol Ivor Novello (Jeremy Northam) and US film director Morris Weissman (Bob Balaban).

Below stairs the pecking order is just as rigorous: Butler Jennings (Alan Bates) rules the roost with housekeeper Helen Mirren backing him up.

To spice things up head housemaid Emily Watson is having an affair with Sir William while there are question marks over Weismann's valet Ryan Phillippe.

Add to this rookie servant Kelly McDonald and mysteriously confident visiting valet Parks (Clive Owen) and the stage is set.

Everything the audience learns is channelled through the servants with lascivious footman Richard E Grant a particularly useful source of information.

It emerges that the curmudgeonly Sir William is resented in several quarters as he holds the purse strings...and there are a few desperate to wrest them from him.

However, when the dirty deed is done there is good reason to look down as well as upstairs to discover the villain (or villainess).

The plot may be more than adequate, but the real pleasure of this piece is the comedy of social manners played against the death rattle of the British class system.

Each character is economically fleshed out with the likes of Stephen Fry (basically reprising Blackadder's General Melchett) and Dame Maggie Smith relied on for laughs.

Altman has triumphed in presenting an awesomely complex gathering in a supremely entertaining mystery where no-one is whom they seem. You'll never play Cluedo again.

Tim Evans