That was not surprising, for Caratacus was well over ninety and he had seemed frail years ago when Ferox had met him in Rome. One-time king of the great tribes of the south, long-time enemy of Rome and ally and friend of his grandfather, the war leader had lost in the end and been betrayed. The divine Claudius had spared him, keeping him in comfortable captivity near Rome. His grandson was a citizen and a soldier just like Ferox, and they had become friends and comrades in those grim days on the Danube, when the Dacians and Sarmatians had cut an army to ribbons.

Ferox began to talk. He could not refuse this request and no one else could have persuaded him so readily. ‘A man does not easily say no to Caratacus,’ his grandfather had often said. There was a power about the man that made anyone feel flattered to have his attention. Ferox told the legate and his friend everything, from the first doubts about the ambush, all that he had seen at the tower and everything that had happened since then. He talked for a long time and they did not interrupt, except once or twice when the legate asked short, direct questions to make matters clearer. Ferox spoke of Gannallius, his story and the man’s death, and of what had happened when he and Vindex had reached Vindolanda, of his regret at thinking all was over once he had made sure that Sulpicia Lepidina was safe.

Most of the hour went as he told his story, and when he finished the legate asked his friend to fetch the sentry from outside the room. ‘Say that the orders will be delayed, but not by long,’ he told the man, and then asked Ovidius to stand by the door and make sure no one disturbed them.

Neratius Marcellus began to pace up and down, and had crossed the room half a dozen times before he spun around. ‘A tribune?’

‘Yes, my lord. Or at least someone pretending to be one. My guess is that the soldiers who slaughtered the men at the tower were real soldiers. Perhaps deserters, but they sound too well equipped for that. No doubt they were bribed, but to commit so great a crime there must have been more. The man giving the orders was able to convince them that they were safe from arrest and execution. Must have made them think that they were on the winning side and that rewards would come, and that he was well enough connected for them to trust him.’

The legate crossed to the wall and came back again. ‘Who?’ he asked, stopping and staring at the centurion, dark eyes hard.