Cato crossed over to him, crouching low as the air was filled with the soft whip of shot flying overhead. A keening rattle was coming from the soldier’s throat. Cato could just make out a shadow on the man’s helmet and reached out to touch it. Sure enough, there was a shallow indentation, the depth of a spoon, where the helmet had taken the full impact of a slingshot. Even if the man’s skull had not been shattered by the blow, the force would have rendered him senseless.

‘Get him to the rear of the tower!’ he ordered one of the legionaries crouching nearby, and then scurried to the back of the gatehouse and glanced down into the fort. The fires in the braziers had been stoked up to ensure that they weren’t extinguished by the drizzle and by their flames he could see men streaming up the wooden steps set into the turf ramparts, before spreading out along the rampart. Their centurions and officers shouted at them to move quickly and keep their heads down as they took up their positions, on one knee behind their shields. The legionaries held the wall either side of the main gate, with the Thracians on each flank. Satisfied that the garrison had responded quickly, Cato turned to beckon to Macro and made his way to the front of the tower. The sound of shot still cracked against the timbers but Cato knew that he must observe the enemy’s progress. Steeling himself, he rose up behind one of the boarded crenellations and looked down at an angle towards the ditch.

The dark slope seethed with shapes and the first of the enemy had already reached the edge of the ditch and were scrambling down towards the shadows that filled the bottom. At once there was the clatter of shards of broken pottery, which were commonly planted in the ditches of forts across the empire, along with other obstacles, to slow attackers down. Cries of pain told of those who had cut their feet or hands on sharp edges. Abruptly the slingshot ceased as the enemy feared hitting their comrades closing in on the defences.

Macro stood up and cupped a hand to his mouth and bellowed along the wall.

‘Prepare the faggots!’

Several men heaved the bundles on to the rampart while others held torches to the braziers, and the moment they were alight their bearers hurried up to join their comrades.

‘Light ’em up!’ Macro ordered. ‘Then over the wall!’