'You'll soon be there.' I said it glibly while wondering which route to take back to the centre of the city.

'Will I?' said Munte in a voice that made me give him my whole attention. 'You've told London that I want to get out. And, guessing the real meanings behind the conversation you had with your wife on my phone, they now know about the evidence I'm providing for you to pinpoint the traitor there.'

'Yes?' I said doubtfully. From the next room there came the solemn melodies of the quartet, the first violin wringing a plaintive song from under his stiffening fingers.

'Are you really such a fool? Someone in London is worrying what you will discover here. They will make quite certain that they hear any news you supply to London. They will then take measures to eliminate both of us.'

'You worry too much,' I said. 'There will be no official report of what I told my wife.'

'I don't believe you. Someone will have to take responsibility for the task of getting us out.'

'My immediate superior. He'll be the only person told. Rest assured that he is not the man we are after.'

'I'm not going home tonight.'

'Then where are you going?'

'We've got a Laube. It's just two tiny rooms and a kitchen but we have electricity, and I won't lie awake all night worrying about policemen knocking on the door. My wife went out there earlier today. She will have some hot soup waiting.'

'Where?'

'At Buchholz, behind the church. It's a huge spread of allotments. Hundreds of people go out there at the weekend even at this time of year.'

'Tonight? It's a long journey to Buchholz. Do you want a ride? I've got a car.'

'You're very kind. It's not such an easy journey by bus and the S-Bahn is quite far away from us.'

I realized that Munte had deliberately introduced the topic with the hope of getting a ride there. 'How soon will you be ready?'

'I must wait for the end of the Haydn. I must tell my friend that his fingers are getting better. It's not true of course, but it's the sort of lie one expects from a good friend.' He smiled bleakly. 'And I will not see any of my friends again, will I?'

First I took Munte to his home in Erkner, a village surrounded by lakes and forests on the extreme eastern edge of the city. I waited in the car ten minutes or more. He returned carrying a small case.

'Family photos, old letters and my father's medals,' he explained apologetically. 'I suddenly realized that I will never return here.'

'Don't take too much with you,' I cautioned.

'I'll throw most of it away,' he promised. 'I should have done that years ago but I never seemed to have enough time.'

I drove north from Erkner on the autobahn with which Fritz Todt – Hitler's chief engineer – had ringed Berlin. The road was in poor condition and more than once the traffic was diverted to single-lane working. Near the Blumberg exit we were waved down by an army motorcyclist, and military policemen signalled frantically with their special flashlight-batons and ran about shouting in the imperious way that all military policemen learn at training school. Civilian traffic was halted while a Russian Army convoy passed us. It took ten minutes for the heavy trucks – some carrying tanks and others with missiles – to pick their way around the broken sections of roadway. It was during this delay that Munte told me a joke. He not only told me a joke, he told me it was a joke before he started it.

'There is a joke that East Berliners have about these neglected autobahns,' he said. 'People say why can't those verdammten Nazis come back and keep their Autobahnen in good order.'

'It's a good joke,' I said.

We waited a long time while the Russian trucks splashed through the rain puddles and thumped their suspensions on the potholes. Munte watched them with unseeing eyes. 'I was driving along here during the Berlin fighting,' he said suddenly. 'It was towards the end of April 1945. The reports said that tanks of the 1st White Russian Front were moving into the northwest part of Charlottenburg and had halted at Bismarckstrasse. And there were unconfirmed reports of Red Army infantry in Moabit. In the car with me I had my younger brother and two of his schoolfriends. We were trying to get to my parents' home near Wannsee before the Russians got that far south. What an idiot I must have been! We didn't know the Russians coming from the southwest had already got to Wannsee. They were past Grunewald and fighting in the streets of Friedenau by that time.'

He was silent until I finally said, 'Did you get there?'

'I was on this same road, this same piece of autobahn. Stopped, just as we're stopped, but by some motorized SS unit. They drained every last drop of gas from my car and pushed it off the road. They were doing that with every car and truck that came along here. I even saw them commandeer two Luftwaffe fuel tankers at gunpoint.'

'You walked home?'

'When the SS men got us out of my car, they looked at our papers. I had my Reichsbank pass and they accepted that without comment. But the three children were ordered to join an assorted collection of soldiers who were being pressed into battle. I objected but they shut me up by threatening to send me into the fighting too.' He cleared his throat. 'I never saw any of those boys again.'

'It's nearly forty years ago,' I reminded him. 'You're not still blaming yourself?'

'I should have stayed with him. He was only fifteen years old.'

'You did what you thought was right,' I said.

'I did what I was told,' said Munte. 'I did it because I was frightened. I've never admitted that to anyone else, but I will tell you truthfully I was frightened.'

The Russian convoy passed and our lane of cars started moving again. Munte sat back in his seat with his head resting against the window. He did not speak again for the rest of the journey, except to warn me when we were getting near to the autobahn interchange for Pankow.

It was late when we reached Buchholz, a village that has become a suburb. The tramlines end in front of the church in a street that is wide enough to be a village square. It was dark and the only light came from a Weinstube where a waiter was sweeping the floor of an empty bar.

Munte told me to turn off at the church. We bumped along a narrow country lane alongside a cemetery. It was dark, but by the headlights' beams I could see that there were trees and bushes on each side of a track that was only just wider than the car. Marking these plots of cultivated land were elaborate little wrought-iron gates, neatly painted fences and trimmed hedges displaying an individuality of taste that bordered on caricature.

Against a horizon faintly pink with the advertising lights of the Western Sector of the city I could make out the squat shapes of the houses and hutments on each patch of ground. Lovingly fashioned by dedicated owners, this was the only sort of private house ownership permitted in the Democratic Republic. And selling such improved property provided a rare opportunity for officially tolerated capitalism.

Munte held out his hand to show me where to stop. I welcomed the careful directions he gave me how to get out of this maze of narrow tracks, for there was not space enough to turn the car or even to avoid another on the same path.

I said, 'Your material is kept quite separate from everything else, Dr Munte. Even if there is a traitor in London, you needn't fear that you'll be betrayed.' The old man got out of the car with a stiff-limbed difficulty that he'd not shown before. It was almost as if he'd aged during the short car journey.

He bent down to look at me. I leaned over the front passenger seat and wound the window down so that I could hear him. 'You have no need to be so devious, Bernd,' he said. 'I intend to go to my office in the morning. I will get the document for you. I am not afraid.'