Ferox had gone right round and was level with the tribune. The legionary came back with a piece of hemp rope cut from the one that they had used to hang the Stallion. He tied the young aristocrat’s hands together.

‘I recall an oath,’ Crispinus said in a low voice, his words bitter. ‘One willingly taken to my father.’

‘You should,’ Ferox said, glaring at him, ‘because it’s the only reason you are still alive. That oath is a burden, but I have a higher oath, a sacred oath that all soldiers take.’ The sacramentum to obey and serve the princeps and the Senate and People of Rome was sworn when a man joined the army, taken in front of the standards, and then renewed at the accession of each new emperor.

‘I serve Rome,’ the tribune claimed. ‘Always Rome.’

‘But not Trajan!’ Ferox yelled and twitched his sword up before putting his other hand on his wrist to push his arm back down. ‘Noble Crispinus, I will not kill you unless I have to, but will leave that task to others. My oath to your father holds that far.’

‘You have no evidence.’ There was doubt in Flaccus’ voice. ‘It is no light matter to arrest a senior officer.’ The protest came after he had let one of his men bind the tribune. ‘How can I be sure you are right?’

‘He has not denied anything, has he?’ Ferox realised his tone was sharp – too sharp for words to a senior officer. ‘My apologies, my Lord Flaccus, but treason is a dirty business and it is hard not to feel rage, especially since I am pledged to this man. But let me explain. Back in the summer the noble Crispinus met with men from the procurator’s staff and arranged for them to demand a higher levy from the Selgovae, and demand it sooner than usual.’

Out of the corner of his eye, Ferox saw the captive tribune frown. He walked around behind him again, still talking. ‘That provoked rebellion, as he knew it would. He got command of the smaller column and made mistakes. He was too slow to cut off the enemy’s retreat, then left the Tungrians high and dry without support. Only luck and your interventions prevented an embarrassing defeat. Then he claims to deal with the king up north, and yet Tincommius’ warriors still join the rebel army. If you had not acted fast and taken the Ninth to guard against attack from the north we might well have lost that battle.’

‘You are too generous in your praise, centurion.’ Flaccus looked pleased.

‘The legate does not think so, my lord, for these are his words. If it were not for one thing, his joy would be untarnished.’