They rode along the line of the Wall, to the east of Banna. Their horses were lively, glad to be working their muscles on this cold morning. They were on the south side of the Wall, so the curtain wall was to their left, the defensive earthwork to their right. They rode into a low sun that glimmered from dew on the churned-up turf of the annexed land. In places you could still see where rows of ploughing had been cut off by the line of the Wall - the last relic of some dispossessed farmer.

They came to a rise, and Brigonius pulled up his horse. From here they could see the Wall sweep across the country from the western horizon to the east, the bright red bands painted on the curtain wall shining in the low northern light, the sandstone of the mile-forts’ flat faces glowing. The Wall was a man-made thing that cut the natural landscape in two.

And the vista wasn’t static, not just a thing of stone and turf, but human too. It was still early but there was already traffic to be seen on the rough causeways leading to the nearest mile-fort, and the smoke from its hearths rose into the crisp air. In one section of the curtain a party of legionaries was busy, with a chime of pick on stone and distant calls like gulls’ cries. Even now the Wall was still being built, rebuilt and refurbished, and it always would be.

Lepidina said, ‘Do you remember how we drove to Rutupiae, all those years ago? My mother told me that the first thing the legionaries did when they landed there was build a wall across that little coastal island, just a rampart of wood and turf to keep out the local barbarians. And now Roman walls have scraped their way across the length of Britain, all the way here, to become ... this. How many miles long - seventy, was it?’

‘Nearer eighty now,’ Brigonius said. ‘Depending on how you measure it - at either terminus it runs into coastal defences which the fleet crews have been building.’

‘Old Xander would have been delighted to see it, if he’d lived.’

‘Well, perhaps,’ Brigonius said doubtfully. ‘But look at this.’ He led her a little further, to the nearest of the mile-forts. You could clearly see where two wings of thick curtain protruded from the outer walls of the fort, but they were built into a much thinner cross-section of Wall. ‘We had to make compromises which Xander would have despised. This mile-fort was already built before the Decision. It was meant to join to a thicker curtain, with those stubby wings. But then we decided to reduce the thickness of the Wall, and so the wings don’t fit. There are other messy bits - places where you can see thicker courses of stone overlaid by thinner.’

‘I see. It’s all rather untidy.’