'You didn't?'

'Are you mad? A prisoner can break a cup and slash his wrists. Don't they teach you anything in England?'

I stood up. 'A young woman gave it to me. She was wearing a blue overall coat. She looked like a secretary but she spoke like a truck driver. She had a very strong Paris accent. She said the coffee and sandwich came with your compliments and would I give it to the man in custody. She said you had to go to a meeting…'

'She wanted to get you out of the way,' said Nicol. He picked up the key and shouted for the uniformed man who was sitting at a desk in the next room. He took the staircase at one leap and I was right behind him.

It was too late, of course. Paul Biedermann was on his knees in the corner, his forehead on the floor like a Muslim at prayer. But his contorted position was due to the muscular contractions that had twisted his body, put a leer on his face and stopped his heart.

Nicol held Biedermann's wrist, trying to believe there was a pulse still beating there, but it was obvious that all signs of life had gone. 'Get the doctor,' Nicol told his uniformed man. A police officer may presume death but not pronounce it.

Nicol picked up the coffee-cup, sniffed it and put it down again. The sandwich was untouched. It was a miserable, dried-up sandwich. It obviously wasn't part of the plan that he should eat the sandwich.

'We'll be up all night,' said Nicol. He had gone white with anger. 'My people will be furious when they hear. When prisoners die in custody it's always police brutality. Everyone knows that. You told me that yourself, didn't you? Can you imagine what the communists will make of this? There'll be hell to pay.'

'The Russians?'

'Never mind the Russians,' said Nicol. 'I've got all the communists I need right here in the National Assembly. I've got more than I need, in fact.'

'It's my fault,' I said, once we were back in his office.

'You're damned right it is,' said Nicol, his anger unabated by this appeasement. 'And that's the way it's going to go down on paper. Don't expect me to cover up for you.' He got a few sheets of lined paper from the drawer and pushed it across his desk towards me. 'You'll have to give me a written statement. I know you'll say you can't; but you'll have to write out something.'

I looked at the blank paper for a long time. Statements are always on lined paper. The police don't trust anyone to write in straight lines. Nicol uncapped a ball-point pen and banged it down on to the paper to hurry me along.

'You're not going to ask me to stay here?'

'Stay here? Me? Keep you here? And explain to my Minister that I let some foreigner go down and murder my prisoner? Write a statement and get out of here, and stay out. The sooner I'm rid of you, the better pleased I'll be. Go and explain it all to your people in London. Although how the hell you will explain it I can't begin to guess.'

The curious rigmarole with the phoney taxi driver began to make sense. The KGB were determined to frame me. It would look as if I put a "sacred" tag on Biedermann, when there was no real investigation in progress, to help him work as a KGB courier. And then, they'd say, the murder was done to silence him.

Now the big conundrum was finally answered. Now I knew what Stinnes had been doing in Mexico City. He'd been sent there to set up Biedermann, and Biedermann was being made ready for this murder for which I'd be blamed. Of course they'd not let Stinnes know the whole plan; that was not the KGB way. Communism has never escaped that conspiratorial climate in which it was born, and in the field even senior KGB officers are kept to their individual tasks. But what care and attention they put into then: tasks. Even while I was sitting there frozen with anxiety, and twisted up with indecision, I had to admire the scheme that had trapped me. The KGB were not noted for their brilliant ideas, but their dogged planning, determination and attention to detail could often make something out of a lousy idea.

Well, the mouse was nearing the end of the maze. Now I knew what trap faced me. But surely to God no one in London Central would believe that I could be a KGB agent, and certainly not one who'd murder Biedermann or MacKenzie in cold blood. But then I remembered the way that Frank had wrung out his conscience to give me a chance to run off to Moscow. There could be nothing more sincere than that; Frank had risked his job, his chances of a K and his pension for me. Even Frank believed I might be guilty, and he'd known me since I was in my cradle. I wouldn't get the benefit of the doubt from those stoney-faced Oxbridge men in London Central.

And when finally I got back to London I was surprised to find a woman in my bed. Well, that's not precisely true. The woman was Tessa my sister-in-law, and she wasn't exactly in my bed; she was sleeping in the spare room. And I wasn't surprised either; there was a note on the hall-stand telling me she was sleeping there.

It was early in the morning. She came downstairs in her magnificent floral dressing gown to find me in the front room. Her long blonde hair was dishevelled and her eyelids were still heavy with sleepiness. There is a curious intimacy about seeing a woman's face without make-up. Tessa looked pale, especially round her eyes where there was usually shadow and darkened eyebrows and blackened lashes. It was the face of a sleepy child but no less attractive for that. I'd never before realized how beautiful she was; George was a lucky man, but there were too many other men equally lucky.

'Bernard. We thought you were never coming back. The children keep asking me…'

'I'm sorry, Tessa. I've come straight from the airport.'

'Nanny gets nervous here on her own, then the children recognize that, and they get frightened too. It's stupid, but she's such a good girl with the children. She doesn't get much time to herself, I moved into the boxroom. You said that I could use it.'

'Of course I did. Any time. Thanks for looking after them,' I said. I took off my hat and coat and threw them on to an armchair. Then I sat down on the sofa.

'Did they give you breakfast on the plane?'

'Nothing fit for human consumption.'

'Do you want coffee?' She fiddled with her hair as if suddenly aware that it was disarrayed.

'Desperately.'

'And orange juice? It will take time for the coffee to drip through.'

'Does David know I'm away so much?'

'He was furious. He threatened to come here and take the children. That was another reason why I stayed here. Nanny wouldn't be able to stand up to him.' Furtively she looked at herself in the mirror and straightened the dressing gown. 'I'm planning to take the children to my cousin's house on Friday… perhaps you'd prefer that I didn't, now that you're home.' Hastily she added, 'She has three children, big garden, lots of toys. We were going to stay there over the school holiday.'

'I have to go back to Mexico,' I said. 'Don't change your plans.'

She bent over me and touched my face in a gesture of great affection. 'I know you love the children. They know it too. You have to do your work, Bernard. Don't worry.' She went into the kitchen and rattled bottles and glasses and cups and saucers. When she came back she was holding a tray with a half-filled bottle of champagne. There was also a jug containing water into which a can-shaped slug of frozen orange juice was trying to melt. 'How do you like your orange juice?' she said. 'Diluted with champagne or straight?'

'Champagne? At this time in the morning I thought they served it in ladies' slippers.'

'It was in the fridge, left over from last night. I split a bottle with nanny but we didn't finish it. The bubbles stay if you put it straight back into the fridge after pouring. I brought a case with me when I came. I had a big bust-up with George and I thought, why leave all the champers there?'