Isolde cynically wondered what choice the farmers had but to pay up. This Duke of the Britains, a Roman commander, seemed to be setting himself up as a warlord of a very old type, with the Wall his seat of power. No wonder this granary had the trappings of a barbarian chief’s hall. Still, perhaps the locals were glad of some order and protection, for any was better than none. And perhaps to many of them, toiling at their land, it made no difference who called himself their lord from one day to the next.

She noticed Tarcho made no mention of the provincial government at Eburacum, nominally still in control of this area. Evidently, ten years after the British Revolution, the political situation had still to sort itself out.

‘Ah,’ Nennius said, ‘but need it have been this way? Need the great tide of empire have drawn back from Britain?’

Tarcho frowned. ‘I don’t know what you mean.’

‘Pelagius preaches of free will,’ Nennius said. ‘Each of us is free to shape his or her destiny. The future is unfixed - it depends on the decisions we make - and so the past too was malleable, dependent on human actions.’ He smiled. ‘There is a passage in Livy, written before the time of Augustus, in which he speculates what might have happened if Alexander had lived on, rather than die so young. Suppose he had turned his attentions west, rather than dissipate his strength in the endless deserts of the east?’

‘He’d have come up against Rome, even then,’ Maria said.

‘Yes—a young but vigorous Rome which would have defeated him - so said the good Roman Livy! The history which seems so fixed to us is actually a fragile tapestry whose weave depended on human whim. And that’s my point. If the decisions of the emperors had been made differently perhaps the eagle would still fly over Britain even now.’ ‘I don’t see how,’ Tarcho said reasonably.

‘Then take one example,’ Nennius said. ‘What if this Wall had never been built? What if the Emperor Hadrian had decided that rather than fix the border here he would complete the conquest of the whole island of Britain, all the way to the north, and devote a legion or two to keeping it? For it was tried, you know, several times, from the age of Claudius himself, and by the Emperor Severus, and later Constantius Chlorus led a force to the far north.’

‘But the land up there is poor and the people are ugly savages who live in bogs,’ Tarcho said practically. ‘What use would it have been? Better to draw a line here.’