ENIGMA, the romantic thriller, has been overshadowed by Kate Winslet, the enigma, in the wake of the marital conflagration of the film's leading lady.

Her understandable no-show at Monday's premiere was the latest distraction but Enigma must now stand - or, rather, fall - on its own merits as a piece of old-school film noir, whose depiction of covert naval intelligence operations is newly topical as President Bush prepares for his Middle Eastern 'crusade'.

Pregnant at the time of filming, and as round as her owlish spectacles, Winslet out of necessity spends much of Enigma seated at a desk, tapping at keys in her frumpy role as plucky wartime codebreaker Hester Wallace at the top-secret Bletchley Park. Typing, it must be said, is every bit as unexciting as watching hackers on computers, and so it needs romantic intrigue and film noir furnishings to save Enigma from becoming too dull a Second World War puzzle.

There are plenty of Enigma variations in Michael Apted's slow-ticking thriller set in grey, grave, Spam-eating 1943. Will Cambridge ace mathematician Tom Jericho (Dougray Scott) crack the latest German Enigma code to give the Atlantic convoys a crucial advantage, or will he crack again after being rushed back to work too quickly from a breakdown?

His mental state had gone awry after his lover, enigmatic femme fatale Claire (Saffron Burrows), rejected him and now she has gone missing. Where is she and why is Jericho being pursued by secret service agent Wigram (Jeremy Northam)? And how come Kate Winslet, in amateur detective mode, is reminiscent of Enid Blyton heroines, Joyce Grenfell and serious Saffron in Absolutely Fabulous all at once?

Northam, witty, urbane and sinister, pinches the movie from the over-worked, uninteresting Scott and Miss Jolly Hockey Sticks Winslet, his sharp attire and hauteur matched by the best lines in Tom Stoppard's script. Northam's acid comments aside, however, Stoppard falls short of his Shakespeare In Love triumph, while John Barry's soundtrack merely ticks over.

Apted tries to inject some much-needed pace and passion to complement the psychological mystery and sense of history in the making, but Scott's late conversion to action hero is unconvincing. What's more, vintage car chases, eccentric office workers, bellowing officers, lunchtime classical concerts and Tom Hollander smoking a pipe that is never alight bring to mind the strange spoof world of the League Of Gentlemen rather than the nostalgic whiff of an old-fashioned war film.