‘We of the sixth, concerned about the practicality of the Wall even before the uprising, have since mounted a major exercise to test its utility. All this is detailed in the report ...’

The idea of the Wall was that in the event of major disturbances to the north, the legions would deploy from their forts in the rear, march through the gates, and meet the enemy in open battle north of the Wall. When detachments of the sixth had actually tried this they hit problems. First you had to walk a few miles to the Wall itself. Then you had to break formation to make your way to one or other of the gates and file through, and just as Tullio himself had anticipated, legionaries in full battle armour found themselves queuing behind farmers’ wagons and herds of sheep. Even on the other side of the Wall you then had to form up again into marching order. During all this time you were terribly vulnerable to attack.

‘It just didn’t work,’ Sabinus said with bold bluntness.

Tullio said, ‘In fact it’s worse. In some places you have to cross the river to get from the forts to the Wall! The Wall’s been my baby, and I hate to say it, but we should pull down the whole wretched thing. We did better under Trajan without a Wall at all.’

Xander stood immediately, plump, anxious, shaking off Severa’s restraining hand. ‘We must finish what we have started,’ he insisted in his heavily accented Latin. ‘You can’t judge the performance of the Wall as a system when it is not completed, any more than you can expect a cart to run on only two wheels. When my design is fully realised—’

‘It’s still not going to work,’ Tullio said bluntly. ‘Because it will still have the flaws we have identified today. A vulnerability from the south. Inadequate crossing points.’

Sabinus nodded. ‘My legate would agree. We have to think too of the longer term implications for the empire as a whole of such a static, frozen frontier. The economic consequences alone—’

Nepos held up a hand to silence him. ‘Now your education is showing, Iulius Sabinus,’ he said dryly. ‘I have only a few years in this chair, and I have to think of the short term, not the long.’

Severa said quickly, ‘In the countryside the Wall has already become a highly visible sign of Roman strength. To abandon it now would be a clear sign of weakness. A retreat.’ Brigonius saw she was trying to manipulate the soldiers’ sensibilities, trying to keep some control of the project.