On the second day, Narses asked to speak with Valens. The duty roster was altered, and they stood watch together.

‘There were three thousand of us that surrendered at Corycus,’ the Persian said. ‘We swore the Roman military oath. They made us leave our horses. We were unhappy about that.’

They were lying close together at the top of the slope. Narses was wearing perfume. It was strong, and had the sweet and spicy aroma of spikenard. Valens had learnt that sometimes it was best to let a man talk. Narses would get to the point eventually.

‘And then there was a problem about the boats. We are forbidden to soil water with human waste.’ Narses smiled. ‘We were given big amphorae. The boats were enormous, several hundred aboard each. Privacy was hard to find in the cramped conditions. It matters to a Persian. Those boats soon stank. The sailors did not love us.’

Narses paused. His dark eyes flicked from the road to the camp and back with the lidless intensity of a bird. He did not look at Valens.

‘A thousand were sent to the garrison in Egypt, the rest sailed first to islands in the Aegean. I went to Lemnos. From there, five hundred of us were ordered to join the imperial field army at Milan. Later we were joined by those who had been held on Rhodes. We went north across the Alps when Gallienus recaptured the province of Raetia from Postumus. There were almost a thousand of us at the battle near Curia, high in the mountains. We were led by our own officers. Things were not bad. I was a scout. After that I became a frumentarius.’

Narses stopped talking.

Again Valens said nothing.

‘The Emperor himself awarded me citizenship. Now I am no longer Narses son of Rastak, but Publius Licinius Narses. I have married a Roman woman. Well, Greek actually. We have a child. They are in Rome. I would return to them.’

For the first time Narses glanced at Valens, but then looked away.

‘I have had news from my father. He does not approve. He has disowned me. It is hurtful. I have a new life, but I am still a Persian.’

At last Narses had raised what was troubling him.

‘You are worried about fighting your own kind?’ Valens said.

Narses fixed his gaze back on the road. His black beard nodded.

‘It is rather late to mention your concern,’ Valens said. ‘You should have told Murena before you left Rome.’

‘I did.’ Narses bared his teeth in a smile which lacked any humour. ‘The little shit told me I had to go – no other soldier in the Roman army had served in the Persian garrison of the Castle of Silence. If my conscience troubled me, I should raise the issue with the Praetorian Prefect. Volusianus himself had instructed Murena to send me on the mission.’

‘Did you?’

‘Of course not.’ Now Narses actually laughed. ‘Would you?’

‘No.’