I realised I was biting the side of my lower lip, a sign of the anxiety I wanted to hide. ‘Emotional. Emotional involvement. That’s the line I wouldn’t cross.’

Maxine was in full-friend mode, pretending that the two of us were just ordinary women exchanging confidences. ‘So as long as it isn’t emotional . . .’ her voice was gentle, understanding ‘. . . physical involvement is okay – to – a – point.’ She tapped the table’s bevelled edge with her index finger, picking it up and setting it down again a few centimetres further along with her last three words, as if counting.

‘Are you asking – if I would sleep with someone for the role?’ I imagined Martin on the other side of the one-way glass, controlling any impulse to sit up straighter or open his mouth wide. He wouldn’t react at all.

‘Now that you mention it.’

I thought I was saying the right thing, but I pictured Martin, no longer able to disguise his interest, sticking his feet out and crossing them at the ankles, leaning back in his chair and shaking his head. Because he could see that I was a fish being reeled in. ‘No, No I wouldn’t.’

‘Are you sure?’ Maxine said this as if she were trying to help me, trying to tell me I had given the wrong answer and should flip it.

‘That would be like prostituting myself for the country. So no.’ My shoe was tapping wildly against the white-tiled floor. I froze, and the absence of noise from it was too noticeable.

‘Even if it was the only way to save your life and the lives of hundreds of others?’

I was flailing, trying to guess what she wanted to hear rather than saying what I thought. Which was the worst thing I could do. ‘If it was for the role. I would be happy to – to go as far as I needed to for the role.’

Maxine’s usual un-reactiveness was gone. She tilted her head, a questioning gesture of moral disgust, as if in disbelief that she’d heard me right. ‘What if you had a boyfriend?’

‘I would go – ahead – and tell him afterwards.’ I was bobbing my head up and down, trying to signal that I meant what I said, that I was trustworthy.

Maxine’s girlfriend pretence had vanished. ‘So you’d cheat to get information.’

I had wanted the job with MI5 more than I ever wanted anything, and I had got so far and so close after multiple tests of my situational judgement and core skills. But it was rushing away from me faster than water down a drain.

Maxine shook her head. She said the most important thing she ever said to me. The thing I would replay all the time.