The buildings, of stone, mudbrick and wood, were a bit more orderly than outside, the narrow cobbled streets between them straighter. But you could see the buildings were old and much repaired. Audax thought two big buildings with two storeys and sparkling tiled roofs must be palaces. Tarcho said they were granaries, where the soldiers stored enough grain to feed them for weeks, in case the barbarians ever attacked. There were more soldiers, including a few who lounged at their posts on the walls. The troops here were a thousand-strong cohort of Dacian origin, Tarcho said, called ‘Hadrian’s Own’. But nowadays most of the soldiers, locally recruited, were British, not Dacian.

Aurelia, her cloak over her arm to keep it off the muddy ground, looked around at the shabby fort with disdain. ‘So this is what has become of the mighty Roman legions!’

‘There were never any legions posted here, madam,’ Tarcho said. ‘In fact strictly speaking there are no more legions nowadays ...’

She shuddered. ‘By Jupiter I wish I’d never come here. If this is all that stands between me and the barbarian hordes of the Highlands I’ll never sleep soundly again.’

The party split up. Thalius, Aurelia and Cornelius were taken to the fort commander’s quarters, a grand old stone building. Tarcho took Audax to a much smaller house of mudbrick and thatch, one of a block. The house belonged to a soldier, an old family friend of Tarcho’s, and it was no barracks, as in former times, but a home. Tarcho’s friend lived here with his wife, two young sons and a whole pack of eager dogs. Audax didn’t know what to make of the noisy bedlam, and the dogs, used to control the slaves in the mine, terrified him. But Tarcho had a quiet word with the soldier’s wife, and she made a fuss of Audax and fed him bread and beef, and Tarcho showed him her husband’s curving Dacian sword, a falx, and he began to feel better.

That night, in a small cot in the corner of a room he and Tarcho shared with the soldiers’ sons, Audax slept well. He felt safe, encased by the walls of the house, and then by the walls of the fort, all of it watched over by soldiers like Tarcho. He thought that Thalius would have said it was a cosy piece of finitude sliced out of an infinite and troubling world.

He was woken in the dark, by a big hand gently shaking his shoulder. Unthinkingly he turned limp, imagining he was back in the mine. If you fought the dirty men they made it worse for you. But he was still in Banna, and it was Tarcho.

‘Come on. Get dressed. I’ve something to show you.’