'I'll come with you,' said the Governor. He heaved himself to his feet.

'That won't be necessary,' said Bret.

'I afraid it will,' said the Governor.

I could see that Bret was becoming more and more angry, so I said to him, ‘I not sure the Governor's security clearance would be sufficient, considering the subject to be discussed.'

There was of course no particular subject on the agenda, but Bret got the idea quickly enough. That's quite true,' said Bret. He turned to the Governor and said, 'Better we keep to the regulations, Governor. From what you say, Stinnes might well make a written complaint about something or other. If that happens, I'd like to make sure you're completely in the clear.'

'In the clear?' said the Governor indignantly. But when Bret made no supplementary explanation, he sat down heavily, moved some papers around, and said, 'I've got a great deal of work to get through here. If you're quite sure you can manage on your own, by all means carry on.'

I went in alone. Erich Stinnes looked content – as much as anyone locked up in Berwick House and left to the mercies of the Governor and his Deputy could have looked content. I knew which room they'd choose for him. It was up on the second floor; cream-painted walls and a plain metal-frame bed, with a print of a naval battle on the wall. That was the room that had the microphones. And the mirror over the sink could be changed so that a TV camera in the next room could film through it.

They'd replaced the light cotton suit he'd worn in Mexico with a heavier English one. It wasn't a perfect fit but it looked good enough. His spectacles flashed with the light from the window as he turned round to see me. 'Oh, it's you,' he said, with no emotion to reveal whether he was happy or disappointed to see me. He'd been standing near the window sketching.

Stinnes was forty years old, a thin bony figure with Slavic features and circular gold-rimmed glasses behind which quick intelligent eyes glittered, and made an otherwise nondescript face hard. He might have been taken for an absent-minded professor, but Sadoff – who preferred his operational name of Stinnes – had been until a few weeks ago a KGB major. Married twice, with a grown-up son who was trying to get into Moscow University, he'd defected and thus got rid of a troublesome wife and been paid a quarter of a million dollars for his services. For such a man, time was not pressing; he was youngish and he was Russian. It was imbecilic to think that 'letting him stew for a few days' would have any effect upon him. I'd never seen him looking more relaxed.

I went to look at his drawing. He must have spent most of the daylight hours at the window. There was a copy of the Reader's Digest Book of British Birds with scraps of paper to mark some of the pages. A school notebook was crammed with his spiky writing. He'd diligently recorded the birds he'd sighted.

A bird identification book was the first thing he'd asked for when he arrived at Berwick House. He'd also asked for a pair of binoculars, a request that was denied. There had been a discussion about whether Erich's birdwatching was genuine or whether he had some other reason for wanting the binoculars. If it was a pretence, he'd certainly devoted a lot of time and energy to it. There were sketches of the birds too, and notes about their songs.

But his observations were not confined to ornithology. He'd pinned a piece of paper to a removable shelf, that was propped against the window frame. It made a crude easel so that he could draw the landscape as seen from his room. The paper was some sort of brown wrapping paper, and to draw he was using the stub end of an old pencil and a fountain pen.

'I didn't know you were an artist, Erich… the perspective looks spot on. Your trees are a bit shaky though.'

'Trees are always difficult for me,' he confessed. 'The bare ones are easy enough, but the evergreens are difficult to draw.' Thoughtfully he added a couple of extra touches to the line of trees that surmounted the hill beyond the village. 'Do you like it?' he asked, indicating the drawing with his hand and not looking up from it.

'I love it,' I said. 'But they won't like it downstairs.'

'No?'

'They'll think you're compromising security by making a drawing of the moat and grounds and the walls and what's beyond them.'

'Then why put me on the second floor? If you don't want me to see over the wall, why put me here?'

'I don't know, Erich. It's not my idea to hold you here at all.'

'You'd put me into a four-star hotel, I suppose?'

'Something like that,' I said.

He shrugged to show that he didn't believe me. 'This is good enough. The food is good, the room is warm, and I can have as many hot baths as I wish. It is what I expected… better than I feared it might be.' This was not in line with what Bret had said about Stinnes and his complaints.

Without preamble I said, 'They released the male secretary. It was political: Bonn. We had enough evidence, but it was a political decision to let him go. We picked up the courier too. I thought we'd got a case officer at first, but it was just the courier.'

'What name?' said Stinnes. He was still looking at his landscape drawing.

'Müller – a woman. Do you know her?'

'I met her once. A Party member, a fanatic. I don't like using people like that.' He held up the pencil to show me. 'Do you have a penknife?'

'Radio operator,' I prompted him. I wondered if he liked holding some bits of information back so that I would feel clever at getting them out of him. Certainly he gave no sign of reticence at telling me the rest of what he knew.

'Correct. She came over to Potsdam for the course. That was when I met her. She didn't know I was from the Command Staff, needless to say.'

'She was working out of London, probably handling my wife's material,' I said.

'Are you sure?' He took my Swiss Army knife from me and sharpened his pencil very carefully. 'If I use my razor blade, it's no good for shaving. They only give one blade per week and always take the old one away.'

'It's a guess,' I admitted. 'Grow a beard.'

'It's probably a good guess. In our system we keep Communications completely separated from Operations, so I can't tell you for sure.' He passed the knife back to me and tried out the pencil on the edge of his picture. He made a lot of little scribbles, wearing it down to give the pencil an especially sharp point. Then he had another go at the trees.

'With two code names?' I said. 'One agent with two codes? Is that likely?'

Stinnes stopped toying with his drawing and looked at me, frowning, as if trying to understand what I was getting at. 'Of course, Communications staff are a law unto themselves. They have all sorts of crazy ideas, but I have never heard of such a thing.'

'And material kept coming after my wife defected,' I said.

He smiled. It was a grim smile that didn't extend to his cold eyes. 'The Müller woman is telling you this?'

'Yes, she is.' I kept it in the present tense. I didn't want him to know that the woman was lost to us.

'She is mad.' He looked at his drawing again. I said nothing. I knew he was reflecting on it all. 'Oh, she might have had more material, but operators never know the difference between top-rate material and day-to-day rubbish. The Müller woman is fooling you. What is it she is trying to get from you?' He made the trees a little taller. It looked better. Then he shaded the wall darker.

Think, Erich. It's important.'

He looked at me. 'Important? Are you trying to persuade yourself that there is another one of our people deeply embedded in London Central?'

'I want to know,' I said.

'You want to make a name for yourself. Is that what you mean?' He looked into my eyes and smoothed his thinning hair against the top of his head. It was wispy hair and the light from the window made it into a halo.