Narcissus pushed his cup away and rose to his feet. ‘Now, I’m afraid I must go. Thanks for your hospitality, Vespasian. And relax. I’m sure the Emperor will be deeply gratified when I report how co-operative you have been.’

‘Before you leave, tell me one tiling.’

‘Yes.’

‘Who is the imperial spy in my legion? I must know who I can trust once we arrive in Britain.’

‘Then he would lose his value to me.’

‘Like being able to report on me, for instance?’

‘Of course.’

‘Then, at least tell me who the traitor is,’ Vespasian asked. ‘I need to know which direction to guard myself against.’

Narcissus tried to look sympathetic. ‘I don’t know. I suspect, but I can’t be sure yet — I need further proof. If I say anything that causes you to treat the people around you differently then the other side’s spy will know we are closing in. Nothing must be done to alert suspicion. You speak to no-one about this matter. Not even your wife. Understand?’

Vespasian nodded. ‘I understand that you’re putting me in danger.’

‘You’re a soldier. Get used to it.’

With that, the imperial chief secretary turned his back on the legate and left the tent, summoning his bodyguard from the shadows with a waggle of a finger. Alone, Vespasian fumed with silent frustration. He had managed to get himself off the hook for the theft of the letter, for the moment. But he was no nearer finding a way out of the dark threads of intrigue that bound him so tightly.

Outside, Narcissus paused. There was no sign that Vespasian had ordered them to be followed. He turned to his bodyguard.

‘Make sure that I’m not tailed. If I call out, come as quickly as you can.’

He walked off quietly, and a few moments later the bodyguard followed, hugging the shadows and keeping a keen eye on his master. Narcissus walked down the line of tribunes’ tents, then paused outside an entrance flap. When he was sure he was unobserved, he entered hurriedly. Inside, the imperial spy was waiting for him, as had been arranged earlier in the day by secret messenger. He rose from his campaign seat to greet the imperial secretary.

‘Keeping well, sir?’

Narcissus grasped the hand that was extended towards him and smiled. ‘Yes, Vitellius, very well. Now, we need a little talk about that scroll I told you about a few months ago. Moreover, I’m curious to know why you omitted to tell me about your arranging to be in the legate’s tent the night it was burgled.’

Vitellius frowned. ‘But I wasn’t in the tent.’

‘That’s not what Vespasian says. He questioned some slave girl who said she had arranged to meet you in there.’

‘It’s not true. I swear it’s not true.’

Narcissus watched him closely and then nodded in satisfaction at the response. ‘All right. I believe you… for the moment. But if it’s not true, then why would she say so? Or why would she be told to say so?’