During the course of the formal occasion Brigonius met her only briefly. There was nothing they could do but exchange pleasantries; Brigonius even found himself asking after her mother's health. But as the evening ended he asked to see her again-just for old time's sake, he said. They agreed to go for a ride together along the Wall the following day. She seemed neither reluctant nor eager, merely polite. And then she was gone, whirled away in the complicated choreography of Roman high society.

That night he could barely sleep. It had been fifteen years, and lying in the dark beside his wife, it seemed that every day of those years hung heavy on his heart.

After the day of the Decision, Claudia Severa had retreated to the sanctuary of the south. Even now Brigonius still had to deal with Severa on matters of business. She had investments in many of the partnerships that had sprung up to serve the needs of the Wall project, including Brigonius's own. He heard rumours that Severa even had a stake in some of the thriving brothels that mushroomed around the Wall forts. She was nothing if not enterprising. But she had lost any real control she had had over the Wall project on the day of the Decision, her final falling from grace in the eyes of the imperial court. And she did not visit again. Brigonius was happy to deal with her only through letters and the dry wordings of lawyers' agreements. He was glad to be shut of Severa.

But when she retreated south she took her daughter with her, and Brigonius had more complex feelings about that. He felt it even more when he heard that while Severa had remained in Britain, Lepidina had gone back to Rome, where she had grown up.

He'd talked this over with Tullio. In one late-night drinking session, as they downed flagons of British beer by the light of the torches that flickered along the Wall curtain, the brusque old Batavian said he understood. 'Of course you miss her. It doesn't matter that you can't have her. You can't have the moon either, but you'd miss its beauty if it were plucked out of the sky, wouldn't you? There are lots of ways to love a woman, Brigonius. You don't need to be waving your cock at them. You can love from afar. I should know.' Tullio's heavy face was a mask of shadows and scars. It was a rare glimpse for Brigonius into the soul of this bluff, competent man, and he wondered how it must have been for Tullio to be taken from his home as a young conscript, transported across the very Ocean, and then to live out his life in such a place as this, so far from home.

Gradually the trauma of that night in the den of Primigenius faded. At last, Brigonius loved again. But he never forgot Lepidina.

And now she was back.

His wife, lying beside him in their bed, was awake too. Cloda, practical and warm, was the daughter of a timber merchant. Her husband had no secrets from her-not even about Lepidina. And so Cloda knew that this spirit of the past had returned to haunt her for a while; and she knew that Lepidina would soon fade into the mists, and she would have Brigonius back again.

Lepidina met him at the fort gate not long after dawn. One of her husband's slaves had prepared horses for them, and a pack of food and wine. It was a bright October morning, only a few days after the autumn equinox, and unseasonably cold; the horses' breaths misted in the air and a thick dew glistened on the ground. But the sun was low, the sky a deep blue, and the light was rich, making the cut stone of the fort walls shine.

And in this setting Lepidina looked wonderful, Brigonius thought helplessly. She wore a sensible leather coat, woollen trousers and heavy sandals. He saw on her neck a medallion he thought he remembered, a fish design done in silver. Her rich strawberry hair, now touched by a little grey, was pulled back from her forehead and tucked under a woollen cap. She didn't seem to be wearing cosmetics, and the natural pink of her skin glowed. She was still beautiful, but it was no longer the beauty of a girl, he thought. This was the wistful autumn beauty of a woman on the cusp of age.

She gazed at him with her deep eyes, and turned away, almost girlish. 'You're staring. You always were a fool, Brigantius-Brigonius.' But there was no reproach in her voice.

'I'm sorry. It's just you look so-'

'If you say I look beautiful I'll punch you. I've given birth to three strapping Roman senators-to-be, and a daughter. She is beautiful. I'm a mother.'

'Very well. You look Brigantian, then.'

That seemed to touch her. 'I do?'

'You look as if you belong here. As if-'

'As if I belong at your side. Is that what you mean?'

For a moment, as he looked into her eyes, the world expanded around them, and the fort, the horses, the patient slave, even the mighty Wall, receded to leave them alone in a pocket universe of their own.

'It is still you,' he said. 'Inside there. Somehow I can see that.'

'Yes. How much baggage we carry around now! Our sagging bodies, our spouses and children, all our business. And yet we are still here.'

He was falling in love with her all over again, he thought, Coventina help him! But the moment passed, and Brigonius tugged on his horse's rein.

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.'