Wacky races: "All the Wild Horses"

The documentary All the Wild Horses makes a feature-length virtue of the kind of eyecatching leftfield event that would merit a five-minute segment on Trans World Sport back in the day. Its subject is the Mongol Derby, an epic seven-day horse race across the largest landlocked country on Earth, arranged by Bristolians, yet cleaving to the route of the first Mongolian postal system - a route designed by Genghis Khan, on what was presumably one of his less bellicose mornings. Riders aim to pass through forty stations en route, selecting a new mount at each from the wild horses corralled there, an element that adds extra chaos to what's already a pretty formidable challenge. The horse whispering involved in these handovers grants director Ivo Marloh time to sketch those personalities gathering for the 2012 competition. There is a plucky young American returning after a time penalty demoted her from first to second the previous year; a pair of Irish jockeys, who spend much of their screen time cursing furiously at their steeds; a black South African greeted by the locals as though he were the first black man ever to reach Mongolia; and a Norwegian whose aim is simply to survive the contest with all her limbs intact ("There's only been one amputation so far"). Enterprising cinema managers may wish to pause the projection after a half-hour to allow punters to place bets on who will cross the finish line first.

In the dust towards the rear is the underaddressed issue of social standing, and who gets to the start line. This Derby's entrants are a lofty mix of fund managers and company directors, drawn from a class who can afford the £400 deposit (before travel and accommodation costs); the British contingent sport accents plummier than Christopher Plummer sucking on a plum in Plumtree. Only the presence of dedicated vets and medical staff reassures us this event is more socially responsible than the Gumball Rally, last decade's overseas jolly of choice for the Henry-and-Henrietta set. That reservation aside, it makes for a hell of a spectacle, one that lends itself to the same big screen that supported myriad Westerns: a hell-for-leather charge across uneven, unpredictable, uncovered ground - with no course markers, straying riders frequently run into packs of camels and get bogged down in sand dunes - which has to be reined in by sundown every night, lest the competitors fall prey to wolves. (It makes the Grand National look like a pony trek.) Marloh does a bang-up job of charting exactly where the runners and riders are at all times - the film is a small model of captioning, which lends the action something of the very specific thriller charge of, say, episodes of 24 - and the physical and psychological toll this event exacts.

A judicious editorial strategy reveals how this race is increasingly a fraught balancing act, a matter of taking much-needed rest, recuperation and fluids at every station without giving whatever advantage you have away. Getting to station 40 upright, without succumbing to dehydration, sunstroke, fatigue or general delirium would be tough enough in itself; getting there before your rivals another thing entirely. (How those original posties managed it, in an era before fructose bars and energy drinks, is a mystery the film never troubles to investigate - though we must assume there was a reason their employer wasn't known as Genghis Khan't.) Essentially, all Marloh is describing here is a straight line - a brisk canter from point A to point B - yet he and his camera team go some distance above and beyond in staying one step ahead of the leading contenders, catching in passing such suffering, endurance, camaraderie and good sportsmanship, not to mention such sterling commitment from the concerned-looking medical professionals dotted en route, that his film can't fail to hook us on some level. I suspect most viewers won't leave All the Wild Horses racing to sign up for next year's event - but you'll almost certainly walk away understanding the compulsions, and admiring the fortitude, of those who do.

All the Wild Horses opens in selected cinemas from tomorrow.