‘Cohort, halt!’ shouted Centurion Hortensius. The cohort drew up, each man shrinking into the shelter of his shield as the whirring started again. The next volley was as ragged as the first and the only casualties this time came from the huddle of prisoners under guard in the centre of the formation.

‘Ready swords!’

The order was followed by a rasping clattering chorus from the dark lines of the legionaries. Then the cohort was still again.

‘Advance!’

The formation rippled forward a moment before settling into a more measured stride. From the front rank of the Sixth Century, Cato could now make out more detail of what lay ahead. The Durotriges had constructed a rough barrier of felled trees and branches that stretched across the narrow floor of the vale and a little way up the slope on each side. Behind this light cover swarmed a dark horde of men. The slingers were no longer shooting in volleys and the whirring of slings and sharp crack of shot were almost constant. Cato flinched from the sound and ducked his head below the rim of his shield as the cohort advanced on the barrier. There were more cries from the ranks of legionaries as the range decreased and the enemy slingers were able to aim more accurately. The gap between the cohort and the felled trees steadily closed until at last the men of the front rank came up against the tangle of branches. On the other side, the enemy had stopped using their slings and now brandished spears and swords, screaming their war cries into the Romans’ faces.

‘Halt! Clear the barricades away! Pass the word!’ Macro shouted, aware that his order would barely carry above the noise.

The legionaries quickly sheathed their swords and began pulling at the branches, desperately tugging and shaking the tangle loose. As the men set about the Durotriges’ makeshift defences, a wild roar of voices from behind the century carried across the vale. Cato glanced back and saw a dark mass swarming across the snow towards the two centuries at the rear of the square formation. Hortensius bellowed out the order for those centuries to turn and face the threat.

‘Nice trap!’ Macro grunted as he heaved a thick limb free of the barricade and fed it back to the men behind him. ‘Get rid of this stuff as quick as you can!’