A less experienced army would have drawn up right there, flushed with excitement at having bested their enemy, trembling with the thrill of having survived and awed by the carnage they had wrought. But the men of the legions continued their advance behind a solid shield wall, swords poised and ready to strike. Most had grown into manhood under the iron will of a military discipline that had stripped away the soft malleable material of humanity and fashioned them into deadly fighters, wholly subordinate to the will and word of command. After only the briefest pause to dress their lines, the men of the Fourth Cohort steadily advanced down the track leading through the vale.

The sun had settled beyond the horizon and the snow took on a bluish tinge as dusk closed in. On either side, the slopes were loosely covered by the broken ranks of the Durotriges, watching in silence as the square trudged past. Here and there their leaders, and the Druids, were busy reforming their men by force of will and cruelly wielded blows from the flat of their blades. War horns brayed out their rallying cries and the warriors gradually began to recover their wits.

‘No slacking!’ Macro ordered. ‘Keep up the pace!’ The first enemy units to re-form began to march after the cohort. The square formation was designed for protection, not speed, and the lightly armed units easily outpaced the Romans. As night fell, the men of the Fourth Cohort were uncomfortably aware of the dark mass of men flowing past them along the slopes in a bid to head off the legionaries once again. And this time, Cato reflected, the Durotriges would have prepared a more effective line of attack.

Night marches are difficult in the best of circumstances. The ground is largely invisible and lays plenty of traps for the unwary foot: a concealed rabbit hole or entrance to a sett can easily twist an ankle or break a bone. The unevenness of the ground quickly threatens to break up a formation and its officers have to move up and down the ranks tirelessly to ensure that a steady pace is maintained and that no gaps appear in the unit. Beyond these immediate difficulties lies the larger problem of route finding. With no sun to guide the men and, in overcast conditions, no stars, there is little more than faith to act upon in setting the line of march. For the men of the Fourth Cohort the problems of night marching were particularly acute. Snow had buried the track they had marched south on some days earlier and Hortensius could only follow the course of the vale, warily assessing each dip and rise in case the cohort was blundering off course. On either side, the sounds of the unseen Britons wore down the exhausted nerves of the men as they dragged their feet forwards.