Abandoned by the retreating Spanish army during the Peninsular War, the gun is an eighteen pounder bronze cannon, thirteen feet long, weighing three tons.

When a group of Spanish partisans come across it two years later they see in it a chance for victory against the French - but first they must haul it across the mountains with nothing but a handful of donkeys and half-starved oxen.

On its epic journey the cannon begins to gain almost mystical significance. For, with the gun, they are no longer a band of Spanish irregulars, they are an army able to take on the cream of Napoleon’s troops…