Outside the house the fort was a pool of shadows. The only sound was the coughing of a soldier on sentry duty somewhere on the fort walls. The sky was a deep blue-grey, a warning of the dawn, and the light reflected from dew on the cobbles.

Tarcho led Audax to a watchtower on the wall, and showed him a ladder. ‘Take care,’ Tarcho whispered. But Audax was used to ladders in the pitch dark, and climbed up more easily than Tarcho himself.

They arrived on the narrow platform at the top of the tower, alone. Up here the air was fresh, crisp with dew, and the customary piss-stink was dissipated by the green smell of growing grass.

Audax looked out over the countryside. The fort was on an escarpment, and looking south he could see how the land fell away to a deeply cut valley where a river gurgled. A steamy stink rose up; the fort’s bath house had been built down there near the water.

And when he looked east and west, Audax at last saw the Wall itself, built into the outer shell of the fort, striding in great straight-line segments across the country. Where the gathering light in the east caught the curtain’s southern face, the pale stone shone. Buildings and forts studded its length, and Audax could see hearth smoke rising, as if it was one gigantic house.

It was centuries old, Tarcho said proudly. ‘My own great-great-great-something-grandfather worked on it. He was called Tullio. I know his name, you see, because it is written on stones set in the Wall itself. He came from Germany. And his sons and grandsons have served on the Wall ever since. Here is the Wall, all patched up, still serving its purpose eight, nine, ten generations later, after most of its builders’ names have been forgotten. What men they must have been in those days, that their vision still shapes our age today! What heroes! And one of them was my grandfather.’

Audax found it impossible to imagine that men had ever built this thing, this Wall. He might as well have been told that men had dug out the valley to the south, or spun the clouds that caught the dawn light overhead.

‘Did anybody live here before the Wall?’

‘Why, I don’t know. Nobody important, just a few hairy-backs. Two hundred years! Think of that.’

Lights sparked along the dark line of the wall, splashes of yellow fire flickering and dying.

Audax was alarmed. ‘What’s that? Is it an attack?’

‘No. They are signal beacons. The watch is changing. All along the Wall soldiers are standing down, and they light their beacons to tell their mates that all is well, all is well ...’

They stayed on the watchtower until the sun had risen. Then they descended into the fort and joined the day’s growing bustle.

XII

XII