The youth waved a hand in dismissal. ‘My uncle said he recognised your sort. He would swear that you were spies, would put money on you being frumentarii.’

So much for our disguise, Valens thought. Still, an ex-centurion, after a lifetime in the army, would have sharper insight than any local.

‘Christians are forbidden to gamble,’ Iudex said. ‘They hold it a sin.’

The youth looked at him, as if he had said something incomprehensible.

‘It does not matter what we are.’ Valens had to put a stop to this. ‘The thing is impossible. The road is too long and hard. There are the mountains of Matiene and the deserts of Arbayestan. You have no horses. Every Persian warrior in the realm would be hunting you. None of you would reach Mesopotamia.’

‘We would be happy to die in the attempt.’

‘It would not only be you that would be dying,’ Aulus said. ‘There is us to consider.’

The young prisoner looked crushed. Then a spark of renewed hope gleamed on his face. ‘Then take me with you.’

‘No,’ Valens said. This was what he had feared.

‘It is a terrible thing to be an exile,’ Clemens said.

‘Listen to him,’ the boy said. ‘Please listen to what he says.’

‘He is not coming with us,’ Valens said. ‘The Persians will hunt him down, and us with him.’

‘Not for days.’ The boy tripped over his words in his eagerness. ‘They will not start to search for me for days. As an engineer, my uncle has more freedom than most. If my absence has been noted, he will tell the Persians that he has sent me on some errand. It will be alright.’

‘Then it will be safe for you to return to him tomorrow,’ Valens said.

‘Please do not send me back.’ The youth was close to crying. ‘You do not know what it is like to live as a slave in an alien land, to have no freedom.’

‘What you take for freedom is nothing but a legal fiction.’ Iudex was measuring his words, as if ladling something weighty. ‘True freedom lies in the soul. Stone walls and iron bars do not make a prison. Mere externals cannot touch the true nature of a man. The lowest captive, although he is whipped and branded, is cruelly beaten and degraded, providing he has a noble and virtuous soul, is as free as any man.’

‘Easy to say when you are not a prisoner.’ Anger was fast overcoming self-pity. ‘How many philosophers are slaves?’

‘Epictetus was a slave,’ Iudex said. ‘He knew of what he spoke.’

‘Enough,’ Valens said. ‘It is time to eat. You can stay here tonight, then in the morning you will go back.’

*

Valens had taken the last but one watch. The sky was getting light when the sounds of men and horses shifting about, and the smell of cooking, made him reluctantly wake after an all too brief sleep.