We are in France in 1918, on the edge of a wood, just behind the battlefront. A group of men are sitting around. They are the members of a crack tank crew: we gradually get to know them, as they engage in desultory conversation or attend to minor chores, while two new arrivals provide some distraction - an American journalist (or is he a spy?) and a Belgian prostitute who has come to offer her wares.

It takes time before the full situation becomes clear. The men are due to take part in a big attack. They recognise that on this occasion they don't stand a chance, and once they have acknowledged their plight one of them proposes that they stage an accident and ditch their tank. Why make a pointless sacrifice when they can live to fight another day? Some of his colleagues go along with him, others violently disagree. Debate is joined.

The play's greatest strength is its feeling for the ways in which shared dangers and professional pride have bound the crew together. It is also fascinating, often horrifying, on the details of early tank warfare. And the author (a seasoned television writer) knows how to create suspense. The procedure which the men use to decide whether or not to quit the battle may strain belief, but you become utterly caught up in it none the less.

Other implausibilities, however, are harder to overlook. The ethnic, social and cultural composition of the crew is almost comically inclusive. Its eight members include a black West Indian and a Sikh. A religious zealot talks about Armageddon, a scientist expounds the new wonders of Einstein's physics. And a high literary note is painstakingly introduced. Two poems by William Blake are read aloud. "He see clear, your Mr Blake," says the black soldier after one of them.

The least plausible aspect of all is the relative absence of military discipline. Democracy prevails, and the commanding officer is only vaguely in charge - which at least accords well with his idealistic socialism. The whole play, in fact, strains to suggest the possibility of something positive emerging from the slaughter, the glimpse of a more just, more harmonious world.

There is no reason why a writer shouldn't treat the First World War mystically or symbolically. But for such an approach to work, you need a sense of struggle and imaginative depth. Here everything comes too easily. The real pain has been bleached away.

It is only fair to add that while you are watching the play its limitations are partly disguised by a string of eloquent performances (Dougray Scott, Ray Winstone and Finbar Lynch are especially good) and by Sam Mendes's accomplished direction.

There are some breath-taking moments - a hooded reconnaissance officer suddenly materialises like an emissary of doom - and there is a powerfully orchestrated climax. But in the end you are still left feeling that the terrible actualities of the First World War have been exploited rather than illuminated.

© The Sunday Telegraph