The Romans only just managed to shelter behind their shields in time as the first volley flew in diagonally from the flanks of the enemy line. With a roar the Durotriges charged home behind the volley. The sharp rattle and crack of the slingshot on the front of the square showed that the slingers had made sure of their aim. But one shot flew over Cato’s head and struck one of the mules harnessed to a wagon in the centre of the formation. It pulverised the eye and the bone surrounding the socket and with a shriek of agony the mule plunged about in its traces, terrifying the other three beasts harnessed to the same wagon. In an instant the wagon swerved into its neighbour and with a protesting groan from the straining axle, it slowly tilted to one side and overturned. The injured were thrown out, scattered beneath the thrashing hooves of the panicked mules. One man, crushed by the side of the wagon, let out a terrible groan before choking on the blood that gushed from his mouth. He fell back lifeless. The shrill braying of the injured mule split the air and made Cato shudder. The wounded on the ground desperately tried to crawl out from under the terrified mules but many were trampled before they could get free. Then another wagon went over and fresh cries of terror and pain rent the air.

‘Cohort! Halt!’ Hortensius shouted. ‘Get those fucking mules sorted out!’

He dived towards the injured animal who had started the chaos and plunged his sword deep into the mule’s throat before tearing the blade free. The blood gushed out. For a moment the mule stood stupidly hanging its head, looking at the crimson pool splashing about its hooves. Then its knees went and it collapsed into the blood, mud and snow.

‘Kill ‘em all!’ Hortensius yelled, and thrust the nearest soldiers towards the terrified animals.

It was all over in a moment and the surviving injured were hauled back into the scant shelter of the undamaged wagons. The cohort could not move any more, not without abandoning its wounded to the bloody savagery of the Durotriges. For a moment Cato wondered if Hortensius was cold-blooded enough to save what was left of his cohort and try to break out towards the relief column. But he remained true to the credo of the centurionate.

‘Close ranks! Close ranks around the wagons!’

The legionaries engaged to the rear and sides slowly backstepped, thrusting out with their swords as the Durotriges stabbed and slashed against the shield wall, driving it back until the Romans compacted into a small knot round the surviving wagons. Those legionaries who stumbled and fell as they gave ground were crushed underfoot and then hacked to death by the Britons. Cato stuck close to Macro, tucked in behind his shield and striking out at the sea of enemy faces and limbs in front of him.