Tarcho, knives glinting at his belt, seemed in his element here. To Isolde’s eyes he seemed more barbarian than Roman, and there was something in his hard, calculating expression she didn’t like.

Maria prompted Tarcho: ‘So you and Nennius share the same grandfather.’

Tarcho spoke around a mouthful of dripping meat. ‘His name was Audax. He was born a slave but died a soldier. He named his son Tarcho, after the soldier who took him in and cared for him. That Tarcho was my father, and he named me for himself.’

‘Ah, yes,’ Nennius said, ‘but Audax came from an old family who hadn’t always been slaves. He was evidently a clever man, and that hereditary intellect seems to have been passed down to his second son, who was my father, called Thalius after another of his patrons. Thalius moved to Rome where I was born, as was my daughter. I’m sure old Audax would have been proud to see you in command of a place like this, Tarcho.’

Tarcho shrugged. ‘Ten years ago I was a serving soldier in the Roman army. Then the British Revolution came. Farm boys in turmoil,’ he said dismissively. ‘We didn’t really know what was going on up here. We just kept the peace along our stretch of the Wall. But there was no more pay ...’

Without pay, some of the soldiers stationed on the Wall drifted away from their posts, some turned mercenary, others resorted to brigandage and robbery - and others, Tarcho said, had gone off to Gaul with their service records in their packs, wistfully hoping to get their back pay. But most of the Wall troops, born and bred where their forefathers had served for generations, just stayed put. This was home; where were they to go?

‘When the dust settled we got new orders from the Duke.’

Isolde asked, ‘The Duke?’

‘The Duke of the Britains.’ The military commander who, under the emperors, had been in command of the Wall and the northern forts that supported it. ‘He was no longer receiving orders from the diocese, or indeed from the prefect in Gaul, or the Emperor.’

The Duke of the Britains, suddenly finding himself free of his chain of command, took control. The troops would continue to function as army units, he ordered; they would continue to protect and police the population. But without central pay it was up to the local people, the farmers, to supply the fort, paying in kind in foodstuffs, materials, animals, labour.

‘There was some grumbling,’ Tarcho said honestly. ‘But then the Picts came. One night they tried to sneak over the Wall, as bold as you please. Well, my men dug out their Roman armour and weapons, and we formed up and sent those brutes packing. After that the farmers were happy enough to cough up, and they turned out to cheer the Duke when he stayed at Banna a few months back ...’