Gosford Park

What better way to start a British film festival than with a quintessentially British film?

A murder takes place at a shooting party in a country house. And in the best traditions of the genre there is a cast to die for. In the drawing room Michael Gambon, Maggie Smith and Charles Dance play bridge while Kristin Scott-Thomas looks on wearily. In the servants' quarters Helen Mirren, Eileen Atkins, Emily Watson and Derek Jacobi swap gossip.

But there is indeed an intruder in their midst. Directing this seemingly quintessential British murder mystery is the all-American Robert Altman, responsible for M*A*S*H and The Player among many others.

But Altman must have been reading his Poirot and watching his Upstairs Downstairs videos. At least the first hour of his film (he co-produced and came up with the idea as well as directing) seems all too conventional and the casting to type – Maggie Smith the acerbic dowager with the devastating one-liners, Kristin Scott-Thomas the exotically bored lady of the manor.

But as the plot all too slowly develops some of Altman's oddball humour and imaginative intellectual probing begins to show. The murder takes place as a house guest Ivor Novello (don't ask!) plays piano and a Hollywood guest is on the phone discussing a plot for a film about a country house murder. It's diverting, mildly.

More interesting is how Altman departs from the conventional mystery to explore not just the motivation of the murderer but the motivations and ethos of life below stairs.

Altman is in safe hands with this cast. Maggie Smith inevitably steals the show, Scott-Thomas is icily sexy, Mirren poignant as a ground-down servant with a secret. But how much better they all would have been with a pacy script and a little more of a hinterland to their characters.

Those Seventies Agatha Christie movies had wit; the cameos were vivid years later. That's not the case here. A clever denouement and a fine cast, even some telling Altman touches, cannot rescue a plodding movie.