Slowly sense returned to the Atrebatans as their Roman officers bellowed orders to end the carnage. The surviving Durotrigans were cowering on the ground or had retreated into deeper water, to escape the savage short swords, and waited for their fate, up to their chests in the bloodstained current.

‘Cato! Cato, lad!’ Here was Macro, beaming face spattered with blood. Beside him, holding the Boar standard was Tincommius, with a gash on his upper arm. ‘We did it!’

But Cato was looking down-river, where a small band of the Durotrigans was escaping along the bank.

‘Not yet, sir. Look there!’

Macro followed where Cato pointed. ‘All right, get your men after them. I’ll tidy up here.’

Cato turned away, splashing back to the edge of the ford, taking care not to stumble over the semi-submerged bodies. On the track he dragged Bedriacus clear of the mêlée and cupped a hand to his mouth.

‘Wolves! Wolves! On me!’

The commanders of his centuries obediently came trotting over, but the Atrebatans had started mutilating the bodies of their enemies.

‘Wolves!’ Cato shouted again.

‘What the hell are they up to?’ muttered Figulus. ‘Oh, no . . .’

Cato turned round and saw one of his men standing above a dead enemy, holding the hair in one hand as he hacked through the last few tendons of the neck with his short sword. Looking round, Cato realised they were all at it. He glanced back at the escaping Durotrigans.

‘Centurion Cato!’ Macro bellowed from the ford. ‘What the hell are you waiting for? Get after them!’

Cato ran back down to his men, grabbed the nearest warrior by the arm and shoved him towards the Durotrigans. ‘GO! MOVE!’

Some of the others looked up, saw what he was gesturing at and started after the enemy, tucking the severed heads under their arms.

‘For fuck’s sake!’ Cato exploded. ‘Leave the heads until later!’

They ignored him and started the pursuit along the riverbank. Cato stopped one man, and, with a grimace, pulled the head out of his hands. The Atrebatan warrior growled a warning and raised his sword threateningly.

‘Tincommius!’ Cato shouted, keeping an eye on the warrior. ‘Get over here!’

The Atrebatan noble pushed his way through the men of the cohorts and approached Cato.

‘Tell ‘em to leave the heads alone.’

‘But it’s a tradition.’

‘Fuck tradition!’ Cato yelled. ‘The Durotrigans are getting away. Tell our men to drop the heads and get moving.’

Tincommius shouted Cato’s order to the cohort, but the only reaction was an angry muttering. By now the Durotrigans had a lead of nearly a quarter of a mile and were fading into the gathering dusk.

‘All right,’ Cato continued desperately, ‘tell ‘em they can keep the heads they’re already carrying. We’ll come back for the rest, I swear it.’