The Eagle (12A)

Left, right, left, right. Kevin Macdonald's macho drama of empire and honour, The Eagle, marches as straight as a Roman road, determinedly, as if to pause on hidden meanings and subtexts might ambush the film's stride. But if it never really soars, there is much in its lowdown grime and grisliness to admire; even its weather becomes quite compelling, a mixture of miserable damp and grey light known in its Highland setting by the resonant word "dreich". Macdonald, rejecting the paintbox shortcuts of CGI, pits real actors against a real climate, and we feel the chill of it in our bones.

Adapted from Rosemary Sutcliff's 1954 children's novel The Eagle of the Ninth – and how I wish they'd kept the mysterious grandeur of that title – it unfolds the story of a Roman centurion, Marcus Aquila (Channing Tatum), who in AD140 arrives in northern Britain to take command of a garrison. He has personal reasons for wanting the post. Twenty years before, his father, Flavius, led the Ninth Legion into this remote territory, and all 5,000 men disappeared, along with the proud standard of their Eagle. It has been a cause of bafflement and shame to the Empire ever since. Marcus, here to restore his family's good name, gets his chance early on when his outpost is attacked by a local tribe, the hairiest bunch of marauding maniacs to carry arms since Braveheart. The forgotten schoolboy in me thrilled to the scene of Marcus leading out his men in the testudo formation – a tortoise of iron shields – to battle with the bloodthirsty hordes.

It's the first indication of the film's willingness to get its hands dirty, jumping right into this melee of clashing steel and piercing cries, not a lot of which I recall from the book. But then these are different times, when standards of screen combat have been set by Gladiator, and more bloodily still, Apocalypto. In his valorous defence of the garrison Marcus sustains a severe leg wound, earning him an honourable discharge and a period of recuperation at the country villa of his uncle (Donald Sutherland). While relaxing in approved imperial fashion – watching men tear one another to pieces in the arena – Marcus manages to save the life of a young Brigantian slave, Esca (Jamie Bell), who thereupon pledges himself to the centurion, even though he abhors this Roman invader and everything he stands for. It is indeed an irony that the heroes of this story are a colonial army known for their brutal suppression of the natives, but the film is not overeager to point up modern parallels. Macdonald alludes to Rome's superpower status by casting Americans as the Romans, and that's as far as it goes: you won't hear echoes of Iraq or Afghanistan.

This looks quite deliberate on the part of Macdonald and his scriptwriter, Jeremy Brock, whose interest lies in the eternal theme of personal honour rather than any political resonance. That theme becomes ever more vexed as the film takes the high road, Marcus having decided to go beyond "the end of the world" and cross Hadrian's Wall into Scotland. He has heard a rumour that the gold Eagle of his father's legion has been sighted up in the wilds, and with Esca as his guide he saddles up and prepares for the worst. Anthony Dod Mantle, who photographed the hot desert colours of 127 Hours, here loads the palette with duns and greens as they journey through vale and glen, the rugged beauty of the land interrupted here and there by turf-roofed hovels and haggard peasants.

Macdonald, who knows all about harsh terrain from the mountaineering exigencies of Touching the Void (2003), first conveys the discomfort of the pair's rain-lashed ride, and then the horror of what awaits them: an encounter with a tribe of hill warriors known as the Seal People, their skin daubed in bluey ash tones, their heads shaven into mohawk plumes – think of them as "The First of the Mohicans". This lot, it transpires, stole the legion's Eagle, and use it as the centrepiece of their nighttime wassails. The Seal leader is played by Tahar Rahim, whose performance lit up last year's prison drama A Prophet and does likewise here as another charismatic brute with a knife. He's so good, in fact, that you start to wonder if Macdonald should have cast him as one of the leads. Channing Tatum – did the casting director think his surname was Latin? – is a game but limited actor, physically right for the part but expressively rather a blank. Jamie Bell is a little more shrewd, and his accent is at least geographically appropriate. But when, under duress, Marcus and Esca switch identities, the actors are not quite crafty enough to put over the ambiguous moral shift in their relationship: I think Tahar Rahim would have carried that off.

The Eagle continually intrigues and absorbs without ever setting the pulse to race. Even when our heroes are being hunted down through the rolling mists, the scene that really catches the eye involves Esca eating an uncooked rat for supper – they daren't risk a fire being spotted – and urging the appalled Marcus to do likewise. The logistics of their fight and flight just don't add up, even if we can believe that the Seal People wouldn't immediately have stuck their heads on a spike. But if credibility wobbles now and then, Macdonald always brings a compelling texture and colour to the tale. It's solid meat-and-potatoes historical drama – meat of a much better quality than anything Esca rustles up. We now know what to say next time a Brigantian invites us to "come dine with me".