With its hooves smacking into the road, the black stallion pranced behind Valens. It was barely under control, but there was a rider on its back. The Persian must have gathered the reins. The horse was heading up the road.

‘Narses, use your bow,’ Valens shouted. ‘Don’t let him escape!’

The break in his concentration was nearly the end of Valens. The officer’s blade struck like a serpent scenting blood. Valens tried to hurl himself aside. He was too slow. The sharp steel rasped across his chest, snapping the rings of his mail.

Valens’s legs had gone from under him. He sat down hard, pain scorching up his back. The officer retrieved his blade, shaped the final blow. Valens scuttled backwards on his arse, the soles of his boots slipping on the gritty surface of the road.

And then the officer wheeled away. Two Romans came at him from either side. Hairan and Decimus, working as a team, intent on taking him down.

Valens left them to it. There was something more urgent.

The Persian had almost mastered the stallion. It had quit its high-stepping sidle, and was breaking into a trot. Narses had his bow in his hand, an arrow nocked.

‘Shoot him!’ Valens yelled.

Narses raised the bow, took aim, drew the string back to his ear. But, arm trembling, he held his pose, and did not release.

The horse had reached a canter.

Valens grabbed the bow, arrow and all, from Narses. With one motion he drew and released. The shaft flew wide.

The stallion was galloping, fast disappearing up the road. Fifty paces, sixty, the distance stretching with each heartbeat.

Valens took another arrow from the quiver. His hands were shaking.

Seventy paces, eighty.

Emptying his mind, Valens took a deep breath, and exhaled, then drew a shallower breath, and held it. With no conscious thought, relying on instinct and the memory in his muscles, he raised, drew and loosed in one motion.

The shaft flew as if guided by the hand of a god. The horse and rider were a hundred paces distant. The arrow knocked the man sideways, the horse shied violently, and the man slid to the ground. Freed from its unwanted burden, the stallion eased to a canter, then pulled up. It turned across the road, and regarded the object on the road with suspicion.

Valens looked back.

The road was littered with Persian dead. The Romans stood isolated from each other, motionless, as if stunned by the return of silence. Narses stood a little apart, looking aghast.

‘Is anyone hurt?’ Valens asked.

Iudex raised a hand like a schoolboy. ‘It is nothing.’

‘Anyone else?’

No one spoke.

‘Hairan, catch that stallion.’ Valens handed the Hatrene the bow. ‘If you can’t, shoot it.’

‘That would be a shame,’ Hairan said.

‘A cruel necessity.’ Valens gathered his thoughts. ‘Decimus, Aulus, get back to the camp, get your mounts, and round up the other loose horses.’