The mounted men disengaged and urged their horses towards the narrow gap. One rider was too slow, and as his horse struggled round a figure leaped up, grabbed him by the arm and wrenched him to the side. Attacker and scout crashed down into the water together and in an instant the enemy warriors closed round the scout with cries of triumph. A gurgling scream rent the air, then it was cut short as spears and swords thrust into the man’s chest, driving the air from his lungs under the crushing impact of so many weapons. The brief distraction allowed Macro and his men to pull back safely into the ranks of the cohort, soaked by the spray from the river and spattered with the blood of comrades and enemies.

Maximius, standing behind the centre of the cohort, met Macro’s wild-eyed gaze with a look of intense and bitter hatred. ‘You’ve lost the ford.’

There was no time for any exchange of words, and Macro turned round and formed up with his men, facing the endless tide of barbarians surging across the ford towards the cohort. They piled into the shields lining the edge of the ford and hacked and thrust at the Romans behind.

At first the legionaries held their ground, exhausted as they were. The relentless years of training paid off in the steady one-two rhythm of punching the shield boss forward, then withdrawing it as the short sword stabbed at the enemy; a pause for the counterstroke and then the sequence was repeated. As long as the line held. If it broke then all the advantages of tight formation and strict training that made them so ruthlessly effective in battle would be lost in an artless test of strength and violent savagery.

As the weight of enemy numbers increased the cohort began to give ground. It was almost imperceptible, but Cato, positioned on the end of the line and not yet engaged, saw the Roman centre begin to bulge backwards. Maximius saw it too and turned to the decurion and the handful of survivors of his squadron.

‘Find the legate and report the situation to him. Go!’

The decurion saluted and turned his horse downriver, ordering his men to follow. He glanced back over his shoulder one last time at his comrades. ‘Good luck, lads!’

Then he was gone, the pounding of hoofs lost against the clatter of weapons and wild shouts of men locked in the desperate struggle.

‘Hold the line!’ Maximius roared, thrusting his sword in the air towards the enemy. ‘Hold the line, you bastards! Don’t give them an inch!’