The floor was covered in straw and rushes, fresh layers piled on the old and all giving off a musty odour. There were sounds from beyond the back wall. Cavalry barracks were built with a line of ten rooms backing on to ten horse boxes. Up above was an attic for storage and the army felt that it was convenient for troopers to be near their horses. It also meant that the rich scents of manure, horse sweat and old leather were everywhere, and there were always flies crawling on the walls or buzzing through the air.

‘You have been with the cohort a long time, I understand.’

‘Sir.’

Ferox had been surprised to learn that the man had served over forty stipendia – fifteen years more than the normal enlistment. It was not his business to ask why, and Longinus did not seem inclined to talk about it. He must be nearly sixty, and yet still remarkably hale.

Instead the centurion asked the man to tell him about the ambush. ‘All that you can remember – no matter how trivial it seems.’

The man’s single eye glinted in the dim room. Ferox felt that the veteran was studying him, amusement mingled with curiosity. His account was precise and matter-of-fact. The decurion was dozy, led them into it, letting the scout get out of sight so that he did them no good. Then the arrows had come.

‘Have you faced archers like that before?’

‘No.’ The eye never left his face. There was a steady grating sound as the old soldier honed the edge of his sword.

Then the sling stones hit them, more arrows, and the screaming charge. Longinus told him about the testudo, the brief respite, of the carriage nearly escaping, until the driver was killed and it tipped over. ‘Got a bit hot then,’ he said. Ferox knew from his own experience how hard it was to remember a fight after it was over, and how it was even harder to recount it. Men who told long detailed stories of battles and heroism were usually making it up.

‘Did you get a good look at the Britons?’ he asked.

Longinus snorted. ‘Too damned good – the buggers were swarming all over us.’

‘Notice anything odd about them?’

The eye was still fixed on him. Longinus stopped sharpening his sword and reached up to scratch his empty eye socket.

‘How did you lose that?’ Ferox asked, letting curiosity get the better of him.

‘Cut myself shaving. Now what did you ask before?’ The man’s Latin was good, for all his slang. He had a Rhineland accent, but did not clip the ends of words or roll his vowels like most of them.

‘You have been in Britannia a while.’

‘Sir.’

‘Well, what did you think about the attackers? Were they like other Britons you have seen?’