I guessed the city was full now of such agents, monitoring troop movements, assessing points of weakness in defences and organising possible resistance for when the time came. I should have felt a sense of power as I delivered the questions or when Donovan urged me to ask him something again, or push him further about the North’s intentions in relation to Saigon, but instead I had a consciousness that I probably had more in common with the captive than my compatriot and didn’t know whether that made me feel pride or shame. But now I try to find some refuge in that sense of irrelevance, telling myself that I was not much more than a cipher in some transaction conducted to rules over which I had little control. And then Donovan played his ace – a family photograph that had been found hidden inside the jacket cover of a book. A woman holding a baby. I watched him place it carefully in the middle of the table, the image still facing him, and he stared at it as if seeing it for the first time. After about thirty seconds he turned it to face its owner. The prisoner barely glanced at it, as if to do so would see them too dragged into the room. Then I asked a series of seemingly innocent questions – what was his wife’s name, what gender was the baby and what age? It didn’t take a lie-detector test to know that the responses to these questions were hasty fabrications delivered with a spurious indifference, starting with a denial that they were his family.

‘Do you want to see them again?’ I asked quietly on Donovan’s precise instruction – I had begun to understand the need not to just say the words but to replicate the tone he himself used – to which the prisoner shrugged his shoulders as if to say it was a matter of little importance.

Donovan placed his hand on the photograph so that only its edges were visible and then slid it slowly towards him until it slipped off the edge of the table and out of sight. Then, taking his wallet out of his pocket, he produced the family photograph I had glimpsed once before and eased it to the middle of the table. But the prisoner barely glanced at it before staring into the distance.

‘Look at it!’ Donovan shouted in French, as if he had taken the cursory glance as a personal insult. Then, as the prisoner obeyed, ‘I want to see them again. I want to go home to them.’

There was a pause while he carefully retrieved his photograph and gently slipped it into his wallet and I was no longer sure what was genuine and what was theatrical performance. Then he replaced his photograph with the prisoner’s and I asked once more if he wanted to see them again.

‘Yes,’ he answered, allowing himself to look longer at the photograph but still not dwelling on it and probably cursing his sentimental moment of weakness that had compelled him to bring it with him. Much later I would come to understand that betrayal is always found in the weakness of the heart, the wellspring of longing that can make both the innocent and the fanatic equally vulnerable.