THE BIG PICTURE / Seeking the self inside: Not guilty - Adam Mars-Jones reviews In the Name of the Father, the Gerry Conlon story

In the Name of the Father (15) is a film that invites a certain amount of smugness from its audience. If it had been made 10 years ago, before the overturning of the verdicts on the Guildford Four, it would have been a campaigning film, urgent and angry - but of course it couldn't have been made then, couldn't have been lustrously cast or adequately financed.

When Bono writes a song for a film, and Sinead O'Connor sings it, it's easy to feel that the whole project is a sort of gala occasion, a ritual of solidarity that flatters its viewers with the idea that they knew all along that the Four were innocent, that 'we' were never deceived. What gets lost is that it was also 'us' who needed to feel safe at the time of the Four's arrests, that 'we' were one source of the pressure behind injustice.

But if In the Name of the Father, released now, can't be all that urgent or uncomfortable, it can be solid and well-crafted, with moments of great power. The film is based on Gerry Conlon's autobiography (written for the screen by Terry George and the director Jim Sheridan) but it doesn't idealise its hero. In an early, set-piece sequence, Gerry ends up, after a chase, throwing Molotov cocktails at armoured cars and prancing in ugly, childish triumph. It all starts with him idiotically miming Hendrix's guitar with a piece of lead pipe he's stealing from a roof, which the security forces unsurprisingly see as a sniper's gun.

When they shoot at him, his vocal mangling of 'Voodoo Chile' becomes the real thing on the soundtrack, and we feel his excitement as well as his fear. We understand how violence polarises, not politically but metabolically, and we could even believe he might find the excitement addictive, in an otherwise uneventual world. Except that the IRA is furious with him for jeopardising its operations, and soon he's being told to pull his trousers down - so that no cloth gets in the wounds when they shoot him in the knees - a threat that may or may not be a bluff.

Daniel Day-Lewis sheds some facial symmetry and physical poise to play Gerry Conlon, becoming plausibly hunched and even scrawny. He gets a suprising amount of sheer fun out of the role, in the film's first hour. When Gerry stumbles on a prostitute's professional accessories in the course of a burglary, he can't resist trying out the whip, the wig and even perhaps the vibrator. With the money he steals there, he buys a memorably ridiculous 1974 wardrobe and returns to Belfast in triumph. He enjoys disrupting the virtuous family atmosphere, singing Gary Glitter's 'I'm the Leader of the Gang (I Am)' to his younger siblings, and showering them with stolen money while his father looks bleakly on.

Giuseppe Conlon, convicted of being part of a supposed terrorist support group, joined his son in prison and died there in 1980. He is played by Pete Postlethwaite, a distinguished character actor more than equal to this co-starring role. When he delivers pious cliches like 'Honest money goes further' as if through dentures of righteousness, it's not hard to understand Gerry's irritation with this man, so proud of everything that keeps him down. Even when their shared ordeal brings them closer, he retains the ability to surprise, reacting to the suggestion that Gerry will look after his mother when widowed with the devastating question, 'You think I'd leave Sarah in your care?'

The film sees Gerry's imprisonment as a period of enforced personal growth. Relentless interrogation over the lavish period permitted by the Prevention of Terrorism Act may seem like a perverse form of therapy, but if the film is to be believed, it had the effect of stripping away Gerry's defences in a way that forced him to confront himself. If the film has a great scene, it is the one of Gerry and Giuseppe being reunited in custody. Gerry hardly takes in the fact that his father, white with lousing powder, has himself been arrested, but launches into an aria of long- standing resentment. Boiled down to its essentials, his speech amounts only to 'You were so good I had no option but to be bad, to prove myself unworthy', and the scene ends with an exhausted embrace and a soundtrack of sorrowing strings, but something raw and very surprising comes through in Day-Lewis's performance.

When the man actually responsible for the Guildford bombing (fictionalised as 'Joe McAndrew' and played by Don Baker) arrives in the same prison as the Conlons, the film dramatises the struggle for Gerry's soul between a good and a bad father in terms uncomfortably reminiscent of an Oliver Stone film. For a while, Gerry lives by the idea that you're better off being guilty, since then at least you get some respect, while Giuseppe, without overt defiance of authority, works indefatigably on the campaign that will eventually clear both their names.

Apart from McAndrew, the prison population is implausibly congenial. What could this jovial Rasta, for instance, distributing jigsaw puzzle pieces impregnated with LSD, have done to merit the blue and yellow uniform of the category A prisoner? Even an apparent hard man, Ronnie Smalls, can have his bluff called, in what must be the film's silliest moment, a ridiculous melting of menace.

As Giuseppe sees it, imprisonment only blocks out the daylight, and - he indicates his head - 'they can't block out the light in here'. In the Name of the Father sets up a string of images to do with the shrouding of heads. On arrest, Gerry is wrapped up in a blanket. At the crucial point of his development, when he could go either way, his bad father, McAndrew, throws a blanket over the film projector (during a showing of the Godfather, would you believe) and sets fire to a warder. Gerry chooses between fathers at the moment when he grabs the blanket from the projector and uses it to smother the flames. Only after this point does Gerry begin to understand what it is like to be his father. He prepares a basin of aromatic inhalant for Giuseppe, and tenderly covers his head with a towel, reminiscing about how puzzling this ritual seemed to him as a child. Now at last he is imaginatively inside his father's head, his sinus and respiratory system.

When the solicitor Gareth Pierce (Emma Thompson) makes the vital breakthrough in her review of her case against the Conlons, it is as a result of a little respiratory trouble of her own. We see her covering her head with a newspaper in a downpour, and then sneezing on a document to be photocopied. The bureaucrat she has been dealing with catches her cold, and on her next visit she is able to get files from his replacement that she would never otherwise have obtained. It's an ill wind, in fact, that blows nobody any good.

In its presentation of Pierce, In the Name of the Father comes closest to the righteous sentimentality that it otherwise keeps in check. It may be that Gareth Pierce fought back angry tears in court, as Emma Thompson has her do, but it was not Pierce's emotions but her hard work that won the Four their freedom, not sympathy but willpower. Thompson's signature expression in the role is of a neutral politeness that is nevertheless urging her conversational partner to become a better person in every way. It is an effective and powerful look, but it needs to be used very sparingly or it starts to imply a sober uniform and a Salvation Army bonnet.

(Photograph omitted)