Xander was no military man, and he was fortunate that the question got bogged down in discussions among Hadrian’s own advisers, who plunged into an evidently ongoing argument about whether a purpose-planned barrier would provide a better long-term solution to the problem of the northern frontier. Hadrian let this discussion run for a while, but no conclusion was reached.

The final objection was raised, diffidently, by an older man, a seasoned soldier who had served in the north. He carefully pointed out that the proposed Wall would cut right through the homeland of the Brigantians. ‘Now, the Brigantian nobles, the survivors anyhow, are powerful figures in the local government,’ he said. ‘They may not take kindly to having their fields sliced in two.’

But nobody among the courtiers took the objections of provincials very seriously.

Hadrian leaned forward, and everybody fell silent. He spoke in convoluted Greek, and Karus translated in whispers for Brigonius. ‘He likes the idea. It is a bold statement. But he is a practical man who counts his sesterces. He built a barrier of turf and wood along the Rhine; would that not be adequate here? After all the threat from the northern British is not as severe as that from the Germans beyond the Rhine.’

It was the crucial objection, and Severa stood. Among the courtiers eyebrows were raised at a woman’s intervention, but they let her speak. ‘A wall of wood and grass will do for a German - but it would never have done for a Greek.’ And she spoke of spectacular long walls the Greeks had built centuries ago, connecting places Brigonius had never heard of: from Athens to the Piraeus, and across narrow isthmuses such as at Corinth. ‘The Wall will be in the best Greek tradition,’ Severa said, ‘but in its mile after mile of shining impenetrable stone it will be a truly Roman statement.’ Xander who had whispered all this to her, looked pleased.

Hadrian looked impressed.

Karus’s eyes were moist. He whispered to Brigonius, ‘That mind, that fire - that heaving chest! Isn’t she marvellous?’

The Emperor was tiring of business. The courtiers sat back, and to a burst of music a troupe of dancers, jugglers and acrobats exploded into the room.

Nepos approached Xander and clapped him on the back, a bold soldier’s gesture that made the little architect flinch. He said in Latin, ‘When I was governor of Thrace my province included such a wall, at Gallipoli. Six centuries old, the historians told me, and still standing today.’ He turned back to the Emperor. ‘You will indeed be building in a grand tradition, Little Greek!’

Hadrian smiled.

But that phrase of Nepos’s - ‘little Greek’ - shocked Severa. ‘What did he call him?’

Nepos had used a Latin word: ‘Graeculus’, Greekling, Little Greek. ‘It’s just a nickname from Hadrian’s childhood,’ Karus said. ‘He always had a passion for all things Greek, even then ...’