'I didn't know. But with you standing there blowing your top it wasn't difficult to guess.'

'They released him an hour ago. Direct instructions from Bonn. The government can't survive another scandal, is the line they're taking. How can they let politics interfere with our work?'

I noted the nice turn of phrase: 'our work'.

'It's all politics,' I said calmly. 'Espionage is about politics. Remove the politics and you don't need espionage or any of the paraphernalia of it.'

'By paraphernalia you mean us. I suppose. Well, I knew you'd have some bloody smart answer.'

'We don't run the world, Dicky. We can pick it over and then report on it. After that it's up to the politicians.'

'I suppose so.' The anger was draining out of him now. He was often given to these violent explosions, but they didn't last long providing he had someone to shout at.

'Your secretary gone?' I asked.

He nodded. That explained everything – usually it was his poor secretary who got the brunt of Dicky's fury when the world didn't run to his complete satisfaction. 'I'm going too,' he said, looking at his watch.

'I've got a lot more work to do,' I told him. I got up from my desk and put papers into the secure filing cabinet and turned the combination lock. Dicky still stood there. I looked at him and raised an eyebrow.

'And that bloody Miller woman,' said Dicky. 'She tried to knock herself off.'

'They didn't release her too?'

'No, of course not. But they let her keep her sleeping tablets. Can you imagine that sort of stupidity? She said they were aspirins and that she needed them for period pains. They believed her, and as soon as they left her alone for five minutes she swallowed the whole bottle of them.'

'And?'

'She's in the Steglitz Clinic. They pumped her stomach; it sounds as if she'll be okay. But I ask you… God knows when she'll be fit enough for more interrogation.'

'I'd let it go, Dicky.'

But he stood there, obviously unwilling to depart without some further word of consolation. 'And it would all happen tonight,' he added petulantly, 'just when I'm going out to dinner.'

I looked at him and nodded. So I was right about an assignation. He bit his lip, angry at having let slip his secret. 'That's strictly between you and me of course.'

'My lips are sealed,' I said.

And the Controller of German Stations marched off to his dinner date. It was sobering to realize that the man in the front line of the western world's intelligence system couldn't even keep his own infidelities secret.

When Dicky Cruyer had gone I went downstairs to the film department and took a reel of film from the rack that was waiting for the filing clerk. It was still in the wrapping paper with the courier's marks on it. I placed the film in position on the editing bench and laced it up. Then I dimmed the lights and watched the screen.

The titles were in Hungarian and so was the commentary. It was film of a security conference that had just taken place in Budapest. There was nothing very secret; the film had been made by the Hungarian Film Service for distribution to news agencies. This copy was to be used for identification purposes, so that we had up-to-date pictures of their officials.

The conference building was a fine old mansion in a well-kept park. The film crew had done exactly what was expected of them: they'd filmed the big black shiny cars arriving, they'd got pictures of Army officers and civilians walking up the marble steps and the inevitable shot of delegates round a huge table, smiling amicably at each other.

I kept the film running until the camera panned around the table. It came to a nameplate fiona samson and there was my wife – more beautiful than ever, perfectly groomed, and smiling for the cameraman. I stopped the film. The commentary growled to a halt and she froze, her hand awkwardly splayed, her face strained, and her smile false. I don't know how long I sat there looking at her. But suddenly the door of the editing room banged open and flooded everything with bright yellow light from the corridor.

'I'm sorry, Mr Samson. I thought everyone had finished work.'

'It's not work,' I said. 'Just something I remembered.'

So Dicky, having scoffed at the notion that I was being kept away from Stinnes, had virtually ordered me not to go near him. Well, that was all right. For the first time in months I was able to get my desk more or less clear. I worked from nine to five and even found myself able to join in some of those earnest conversations about what had been on TV the previous evening.

And at last I was able to spend more time with my children. For the past six months I had been almost a stranger to them. They never asked about Fiona, but now, when we'd finished putting up the paper decorations for Christmas, I sat them down and told them that their mother was safe and well but that she'd had to go abroad to work.

'I know,' said Billy. 'She's in Germany with the Russians.'

'Who told you that?' I said.

I hadn't told him. I hadn't told anyone. Just after Fiona's defection, the Director-General had addressed all the staff in the downstairs dining room – the D-G was an Army man with undisguised admiration for the late Field Marshal Montgomery's techniques with the lower ranks – and told us that no mention of Fiona's defection was to be included in any written reports, and it was on no account to be discussed outside the building. The Prime Minister had been told, and anyone who mattered at the Foreign Office knew by means of the daily report. Otherwise the whole business was to be 'kept to ourselves'.

'Grandpa told us,' said Billy.

Well, that was someone the D-G hadn't reckoned with: my irrepressible father-in-law, David Kimber-Hutchinson, by his own admission a self-made man.

'What else did he tell you?' I asked.

'I can't remember,' said Billy. He was a bright child, academic, calculating and naturally inquisitive. His memory was formidable. I wondered if it was his way of saying that he didn't much want to talk about it.

'He said that Mummy may not be back for a long time,' said Sally. She was younger than Billy, generous but introverted in that mysterious way that so many second children are, and closer to her mother. Sally was never moody in the way Billy could be, but she was more sensitive. She had taken her mother's absence much better than I'd feared, but I was still concerned about her.

'That's what I was going to tell you,' I said. I was relieved that the children were taking this discussion about their mother's disappearance so calmly. Fiona had always arranged their outings and gone to immense trouble to organize every last detail of their parties. My efforts were a poor substitute, and we all knew it.

'Mummy is really there to spy for us isn't she, Daddy?' said Billy.

'Ummm,' I said. It was a difficult one to respond to. I was afraid that Fiona or her KGB colleagues would grab the children and take them to her in East Berlin or Moscow or somewhere, as she once tried to. If she tried again, I didn't want to make it easier for her to succeed, and yet I couldn't bring myself to warn them against their own mother. 'No one knows,' I said vaguely.

'Sure, it's a secret,' said Billy with that confident shrug of the shoulders used by Dicky Cruyer to help emphasize the obvious. 'Don't worry, I won't tell.'

'It's better just to say she's gone away,' I said.

'Grandpa said we're to say Mummy's in hospital in Switzerland.'

It was typical of David to invent his own loony deception story and involve my children in it.

'The fact is that Mummy and I have separated,' I said in a rush. 'And I've asked a lady from my office to come round and see us this afternoon.'