Enigma

At first glance, this is an old-fashioned British picture, harking back to war movies of the Fifties, in which emotions are buttoned, lips stiffened and spies discovered under beds. On second glance, it's too clever to be categorised by the cut of its tweed. Tom Stoppard's script, adapted from Robert Harris's best seller, is both witty and intelligent. Despite the suspicion that someone thought what fun it might be to make a John Buchan pastiche, as exemplified by Jeremy Northam's performance, there is so much more going on here that would fit into Richard Hannay's rucksack.

The hero is anti, for a start. Tom Jericho (Dougray Scott) does not fit the Kenneth More mould. He's had a breakdown, he's not public school and he can't be fished with protocol. He knows he's some kind of mathematical genius, who can do crosswords in a couple of minutes, but this doesn't impress him. He's not a games player. He works alone and he walks alone. Except there was a girl, Claire (Saffron Burrows), who broke his heart. Or would have, if he had one.

Tom is brought back to Bletchley Park in 1943, after being unofficially dismissed for insubordination, because the Germans discovered their codes had been cracked and so rewrote them. A huge convoy is in the Atlantic on its way from America and there are strings of U-boats waiting. In order to save the merchant fleet, these new codes must be broken.

Bletchley is a big house in the country, taken over by the War Office and transformed into a think tank. Oxbridge graduates, assorted swots and upper-class gels, who don't mind wasting their education on brain-numbing secretarial work, operate there. Because of the regime of strict secrecy, noone knows what the other person does, and so when Tom finds out that Claire has disappeared, even Hester (Kate Winslet), who shares a house with her, hasn't a clue where she's gone.

This is one mystery amongst many. Stolen cryptograms are unearthed under a floorboard in Claire's room. A suave secret service agent (Northam) turns on the charm, as if that would make the slightest difference to a disaffected class warrior like Tom. There is a sense of urgency in the air. The enigma codes must be unlocked to save the convoy. Has Claire been murdered? Is there a German mole at Bletchley? What is it about Hester that Tom grows to like?

Stoppard and director Michael Apted weave a web of intrigue, suspicion and, for God's sake, romance into what might have been as incomprehensible as a computer hacker's notebook. Winslet is wonderful in specs and sensible shoes. Scott is different. Being a chippy, love sick depressive is not exactly movie star material, but he makes a man of Tom Jericho, a man you would want to meet.