There was nothing to do but wait. The men had largely ignored Valens. The two easterners with whom he had fought – Narses the Persian, and Zabda from Palmyra – had looked at him with open malevolence. Only Iudex and Hairan had offered their company.

‘Severus docked your next two months’ pay for not reporting yesterday,’ Iudex said.

Hairan snapped his fingers. ‘That is all money means.’

‘Yet you needed it to pay your whores. I thought you had a sterner morality. Do you Arabs not put to death those even suspected of adultery?’

‘That may be the case among the primitive tent-dwellers.’ Hairan twirled the ends of his luxurious moustache. ‘We men of Hatra take full enjoyment of the pleasures of the flesh. We pride ourselves on our prowess. Not that we lack morals. Among us there is a law that anyone who steals a trifle, if only water, is punished with stoning.’

Valens glanced over at Zabda, the long-faced man from the bar.

‘Yes,’ Hairan said, ‘that Palmyrene needs watching.’

‘And boys?’ Iudex had his notebook out.

‘Never!’ Hairan looked outraged. ‘Be careful, brother. Beyond the Euphrates, if a man is accused of such intercourse he will take revenge, and not shrink from murder.’

Iudex wrote quickly. His head was bent over the hinged wooden blocks, the stylus, tiny in his big fingers, pressing neat characters in the wax.

‘We do not share the tastes of ugly old Aulus.’ Hairan nodded to where the quartermaster was fussing over the loads of the mules. ‘Gauls like him are terrible pederasts. They see no shame at all in their infamy.’

As if at a secret signal, everyone waiting in the street got to their feet, checked their belongings, and began to close up, shuffling towards the bridge.

Conscious that he should assert his authority, Valens went to the head of the caravan.

There were only two customs men at the post. Goats and sheep bound for slaughter were driven towards one. Produce – olive oil and grain, animal fat and pine cones – presented to the other. There was much delay and argument. Everything had to be taxed and tempers became frayed. Peasants from the villages in the territory of Zeugma were exempt, and traders in goods like salted fish and rock salt, items most unlikely to be local, volubly tried to claim the exemption.

When the caravan finally reached the customs, things went no quicker. Even when Valens had persuaded the official that only two of the mules carried trade goods, the remainder being loaded with personal provisions not for sale, the question arose if a mule should be taxed as if a donkey or a camel. Eventually Hairan intervened, speaking fast, in what Valens thought was Aramaic. Some coins changed hands, and the mules were rated as low-tax donkeys. Further coins, more openly given, settled the tariff, and they were free to proceed.