'That's the sort of little black book I wouldn't like to keep,' I said.

'Incriminating. Right. That's it exactly. I wish I could get that fact into the heads of the idiots who run this bureau.'

'You're not recording any of this?'

'Let me tell you something in confidence,' said Lenin. 'I was on the phone to Moscow an hour ago. I pleaded with them to let me interrogate you my way. No, they said. The KGB Colonel is on his way now, Moscow says – they keep saying that, but he never arrives – you are ordered not to do anything but hold the prisoner in custody. Stupid bastards. That's Moscow for you.' He inhaled and blew smoke angrily. 'Quite honestly, if you broke down and gave me a complete confession about having an agent in Moscow Central Committee, I'd yawn.'

'Let's try you,' I said.

He grinned. 'What would you do in my place? This KGB Colonel will take over your file when he gets here tomorrow morning. Do you think he'll give me any credit for work done before he arrives? Like hell he will. No, sir, I'm not going to dig anything out of you for those Party bigshots.'

I nodded but I was not beguiled by his behaviour. I'd long ago learned that it is only the very devout who toy with heresy. It's only the Jesuit who complains of the Pope, only the devoted parent who ridicules his child, only the super rich who pick up pennies from the gutter. And in East Berlin it is only the truly faithful who speak treason with such self-assurance.

They took me downstairs at seven o'clock the next morning. I'd heard cars arriving shortly before, and men shouting in the way that guard commanders shout when they want to impress some visiting hotshot.

It was a plush office by East European standards: modern-design Finnish desk and chairs and a sheepskin rug on the floor. A faint aroma of disinfectant mingled with the cheap perfume of the floor polish. This was the smell of Moscow.

Fiona was not sitting behind the desk; she was standing at the side of the room. My friend Lenin was standing stiffly at her side. He'd obviously been briefing her, but Fiona's authority was established by the imperious way in which she dismissed him. 'Go to your office and get on with it. I'll call if I want you,' she said in that brisk Russian that I'd always admired. So the so-called Erich Stinnes was a Russian – a KGB officer no doubt. Well, he spoke bloody good Berlin German. Probably he'd grown up here, the son of an occupier, as I was.

Fiona straightened her back as she looked at me. 'Well?' she said.

'Hello, Fiona,' I said.

'You guessed?' She looked different; harder perhaps, but confident and relaxed. It must have been a relief to be her real self after a lifetime of deception. 'Sometimes I was sure you'd guessed the truth.'

'What guessing was needed? It was obvious, or should have been.'

'So why did you do nothing about it?' Her voice was steel. It was as if she were pushing herself to be as robotic as a weighing machine.

'You know how it is,' I said vaguely. 'I kept thinking of other explanations. I repressed it. I didn't want to believe it. You didn't make any mistakes, if that's what you mean.' It wasn't true, of course, and she knew it.

'I should never have handwritten that damned submission. I knew those fools would leave it in the file. They promised…'

'Is there anything to drink in this office?' I asked. Now that I had to face the truth, I found it easier than dealing with the dread of it. Perhaps all fear is worse than reality, just as all hope is better than fulfilment.

'Maybe.' She opened the drawers in the desk and found an almost full bottle of vodka. 'Will this do?'

'Anything will do,' I said, getting a teacup from a shelf and pouring myself a measure of it.

'You should cut down on the drinking,' she said impassively.

'You don't make it easy to do,' I said. I gulped some and poured more.

She gave me the briefest of smiles. 'I wish it hadn't ended like this.'

'That sounds like a line from Hollywood,' I said.

'You make it hard on yourself.'

That's not the way I like it.'

'I always made it a condition that nothing would happen to you. Every mission you did after that business at Gdynia I kept you safe.'

'You betrayed every mission I did, that's the truth of it.' That was the humiliating part of it, the way she'd protected me.

'You'll go free. You'll go free this morning. It made no difference that Werner demanded it.'

'Werner?'

'He met me with a car at Berlin-Tegel when my plane landed. He held me at pistol point. He threatened me and made me promise to release you. Werner is a schoolboy,' she said. 'He plays schoolboy games and has the same schoolboy loyalties you had when I first met you.'

'Maybe that was my loss,' I said.

'But not my gain.' She came closer to me, for one last look. 'It was a good trick to say you'd cross first. It made me think I might get here in time to catch Brahms Four; your precious von Munte.'

'Instead you caught me,' I said.

'Yes, that was clever, darling. But suppose I hang on to you?'

'You won't do that,' I said. 'It wouldn't suit you to have me around. In a Soviet prison I'd be an impediment to you. And an imprisoned husband wouldn't suit that social conscience you care so much about.'

'You're right.'

'At least you're not trying to find excuses,' I said.

'Why should I bother? You wouldn't understand,' she said. 'You just talk about the class system and make jokes about the way it works. I do something about it.'

'Don't explain,' I said. 'Leave me something to be mystified about.'

'You'll always be the same arrogant swine I met at Freddy Springfield's party.'

'I'd like to think I was just a little smarter than the man you made a fool of then.'

'You've got nothing to regret. You'll go back to London and get Dicky Cruyer's desk. By the end of the year you'll be running Bret Rensselaer out of his job.'

'Will I?'

'I've made you a hero,' she said bitterly. 'You made me run for cover, and at a time when no one else suspected the truth. Until you phoned about the handwritten report, I thought I could keep going for ever and ever.'

I didn't answer. I kicked myself for not acknowledging the truth years before – that I had been Fiona's greatest asset. Who would believe that Bernard Samson would be married to a foreign agent and not realize it? Her marriage to me had made her life more complicated, but it had kept her safe.

'And you rescued your precious agent. You got Brahms Four home safely enough to make all your other agents breathe easily once more.'

I still said nothing. She might be leading me on. Until I was sure that the Muntes were safe, I preferred to play dumb on the subject.

'Oh, yes. You're a professional success story, my darling. It's only your domestic life that is a disaster. No wife, no home, no children.'

She was gloating. I knew she wanted to provoke me into an outburst of bad temper. I recognized that tone of voice from other times, other places and other arguments. It was the tone of voice she sometimes used to criticize Werner, my grammar, my accent, my suits, my old girlfriends.

'Can I go now?'

'The arresting officer – Major Erich Stinnes – is taking you to Checkpoint Charlie at nine o'clock. The arrangements are all made. You'll be all right.' She smiled. She was enjoying the chance to show me how much authority she had. She was a KGB Colonel; they would treat her well. The KGB look after their own, they always have done. It's only the rest of the world they treat like dirt.

I turned to go, but women won't let anything end like that. They always have to sit you down at the table for a lecture, or write you a long letter, or make sure they have not just the last word but the last thought too.

'The children will go to the best school in Moscow. It was part of the arrangements I made. I might be able to arrange that you have a safe passage to see them now and again, but I can't promise.'