It's bare knees against articulated metal pyjamas in Mel Gibson's latest butchfest. Adam Mars-Jones referees; BRAVEHEART Mel Gibson (15)

First Rob Roy and now Braveheart: suddenly Hollywood has the hots for Scotland, for misty glens, broad knees and a history of virile defeat. Braveheart is set around the year 1300, and tells the story of William Wallace, who scored notable successes against the English at Stirling and York, before being betrayed and then executed in Smithfield, London, where a plaque outside Bart's Hospital commemorates him.

Wallace in Mel Gibson's film is an almost preposterously rounded character. He is a man of peace, reluctantly taking up arms against injustice. He is a tender lover, faithful to his first passion. He is educated and well travelled, speaks at least three languages and has been to see the Pope, yet he is incorruptibly a democrat. His fighting skills are remarkable, but it is by virtue of tactical thinking that he defeats larger, better equipped forces. This generosity of character drawing is almost inevitable when you take a screenwriter who shares a surname with his hero (Randall Wallace) and feels a spiritual, if not literal kinship ("Spirit is greater than fact", as he says), and then expose him to the expert advice of the lineal descendants of Clan Wallace, who are unlikely to have spent the centuries from 1300 to now looking for their ancestors' feet of clay. William Wallace in the film has no tragic flaw. His only mistake is to assume that people with a sense of honour will share his ideal of freedom for Scotland the moment they hear of it.

Mel Gibson, starring as well as directing, has to think of his image, and consequently plays Wallace as the only clean- shaven man in Scotland. The effect, when combined with long matted hair, suggests someone in a medium-ranking heavy metal band. There are times in Braveheart, too, when he over-indulges in his acting mannerisms, the grins and twinkles of his stardom. At one point, when the Scottish nobles honour him and his comrades, and one of them is uncomfortable to be receiving a medal that seems more like a necklace, Gibson even makes his eyes go very wide, to signify play along, I have a plan, I'll explain later, as if he were still buddy-buddying with Danny Glover from the Lethal Weapon series.

Gibson overworks his Adam's apple in a big emotional scene with Sophie Marceau, hardly surprisingly given the situation: she plays the Princess of Wales, sent with an offer of peace by the Machiavellian English king (though Machiavelli hasn't been invented yet), played with much relish by Patrick McGoohan. The princess's home life is unsatisfactory, since her husband is not really the marrying kind, and, indeed, directed glances of flaming faggotry at his favourite, Philip, during the wedding ceremony. So she warms to this romantic rebel. "Why do you help me?" he asks her a number of times, and she replies: "Because of the way you're looking at me now." He tells her the story of his first love, and soon she's consoling him in a very real way. So, all things considered, there's quite a lot of implausibility to swallow in this encounter, and no wonder Mel Gibson's Adam's apple is so busy.

In the past, Gibson's bottom has been an important underpinning of his persona (in one of his vehicles, Bird On A Wire, it was so extensively featured that it threatened to upstage him altogether), but here he keeps it under wraps. Or rather, Braveheart doesn't contain a buttock solo, though there is a sort of buttock ensemble. The Scots at Stirling express their defiance by first flashing and then mooning at the English, gestures which the kilt makes easy as well as politically expressive.

The mixture of high ideals and rough manners is irresistible, but it is actually the basic flaw of Braveheart that identification with the Scots is so easy. Who wouldn't side with manly virtue against vicious effeteness, and with bare knees against the articulated metal pyjamas that Charles Knode has designed for the English army (fully as plausible as an example of 14th-century craftsmanship as, say, a combine harvester). The Scots in Braveheart combine Roundhead politics with Cavalier stylishness and joie de vivre. They're like Southerners in the American Civil War without the taint of slavery, enlightened rednecks. To sustain interest over nearly three hours, a film needs to invest more subtlety in conflict of character.

There is an element of this in the character of Robert the Bruce, who is drawn to Wallace's ideals and envies his inspirational qualities as a leader, but still feels the pull of his own aristocratic interests, which would be better served by alliance than defiance of England. Braveheart would have a stronger structure if Bruce's role was larger since, after all, Wallace was the John the Baptist of Scotland's independence rather than its Messiah, and it was Bruce who later changed history at Bannockburn. As it is, Bruce is played by an actor, Angus MacFadyen, making his film debut, who is regularly outshone by Ian Bannen as his father or, more accurately, by Bannen's make-up, since Bruce senior is a leper who becomes more disfigured by the minute.

In the absence of satisfying moral dilemmas, Braveheart is an action film with an unhappy ending rather than the tragedy it would like to be. The film has excellent battle sequences, and many rather absurd touches. When the Princess of Wales comes to say goodbye to Wallace, she brings a little vial which will numb him during torture. He says he wants to keep his wits unfuddled, which is well butch; she pleads with him, he agrees, and he drinks it. They kiss, she leaves and he spits it out. This is butchness beyond the call of duty, but Clan Wallace must be delighted.

The big tune that James Horner has composed for the film is a variant of Holst's "I Vow To Thee My Country" - a patriotic hymn, but hardly a Scottish one. A similar incongruity recurs even more forcibly during the protracted sequence of Wallace's execution. Wallace, his mind unclouded as he wished, refuses to repent or to plead for mercy, and is tortured at some length (in other words, racked). He offers his body as an emblem of the indomitability of Scotland. It's a mistake, in a film with so little actual Scottish involvement, to pretend in this way to be concerned with a national essence, rather than serving up a Hollywood action adventure in a Scottish source.

n On general release from Friday