Directed by Peter Weir. Starring Jim Sturgess, Colin Farrell, Ed Harris, Saoirse Ronan, Mark Strong 12A cert, gen release, 133 mins

THERE'S NO reason this film shouldn't have been a classic. Peter Weir, the veteran Australian director, has a formidable talent for bringing twilit magic to mainstream projects. The world would be a poorer place without Gallipoli, Witnessand Master and Commander.

The Way Backhas a pretty decent cast: Colin Farrell, Ed Harris, Jim Sturgess and Saoirse Ronan all turn out for a gruelling stomp. The film also hangs around a cracking (if vigorously disputed and frequently implausible) tale from recent history.

Based on a book by Slavomir Rawicz, the film concerns the breakout from a Siberian Gulag in 1942. If the script is to be believed, a party of prisoners, after strolling nonchalantly into the snow, managed to progress from the northern reaches of the Soviet Union to sanctuary in British- occupied India. Now, this sounds like something worth seeing.

To be sure, there are worse things you could do with your time, but, dragged down by a pedantic script and burdened with crude characterisation, The Way Backfalls far short of fulfilling its daunting potential. Each actor is given little more than a rough adjective with which to work.

Harris, playing a rogue American, is enigmatic. Farrell, as a gangster – Stalin tattooed on his chest – is animalistic. Sturgess, a Pole framed for spying, is charismatic. Ronan’s character comes across as a mess of contradictions: a homeless waif who, though making a living on street corners, still seems to have retained an unlikely sweetness. All do what they can with very thin material.

It doesn't help that, every now and then, they are asked to stop and read out a few pages of Soviet History for Dummies. "The Gulags were a system of prison camps that allowed the USSR to practice a form of slave labour," nobody really says. "Mongolia is a mountainous country in east Asia that features many stunning views."

The shame is that Weir frequently manages to show traces of what might have been. Allowing yawning vistas to fill the screen, staging exciting set-pieces on treacherous ice-flows, he demonstrates that, if permitted a more nuanced script, he may well delivered another characteristically ambiguous epic. As things stand, we are saddled with an only slightly cheesy Boy's Ownadventure story. So many squandered opportunities.

Opens December 26th