'No,' I said. Not far away from us, a six-piece wind band had assembled. Now they were making all those sounds musicians have to make before playing music.

'You want to see the writing. You want to see who is the traitor in London Central.'

'I know who it is,' I said.

'You've guessed, you mean.'

'I know. I've always known.'

'I risked my freedom to get it this morning,' he said.

'I'm sorry,' I said. I picked up the envelope and toyed with it as I reasoned out what to do. Finally I handed it back to him. 'Take it to London,' I said. 'Give it to Richard Cruyer – he's a slim fellow with curly hair and chewed fingernails – make sure no one else gets it. Now we must go. The police seem to have traced us here. They're the same ones who went to Buchholz.'

'My wife – is she safe?' He got to his feet in alarm. As he did so, the wind band began playing a drinking song.

'Yes, I told you. But we must hurry.' I could see them arriving now. I could see Lenin, with his long brown leather overcoat and his little beard. He was wearing a brown leather cap too, and metal-rimmed glasses. His face was hard and his eyes were hidden behind the bright reflections of his lenses. Alongside him was the young Saxon conscript, white-faced and anxious, like a child lost in a big crowd. It was unusual to have a conscript in such a team. His father's influence must be considerable, I thought. The four policemen had stopped suddenly at the end of path, surprised, just as I had been upon first catching sight of the multitude.

The band music was loud. Too loud to make conversation easy. I grabbed Munte's arm and moved him hurriedly into a crowd of men who had linked arms and were trying to dance together. One of them – a muscular fellow with a curly moustache – was wearing striped pyjamas over his clothes. He grabbed Munte and said, 'Komm, Vater. Tanzen.'

'I'm not your father,' I heard Munte say as I stood on tiptoe to see the policemen. They had not moved. They remained on the far side of the beer garden, bewildered at the task of finding anyone in such a crowd. Lenin tapped one of the older men and sent him down the line of men waiting to buy beer. He sent the fourth man back along the path; no doubt he was going to bring more men from the minibus.

For the second time, Munte disengaged his arm from that of the man in pyjamas. 'Ich bin vaterlos,' said the man sorrowfully. The 'fatherless' man pretended to cry. His friends laughed and swayed in time with the om-pah-pah music. I grabbed Munte and pushed through the dancers. Looking back, I caught sight of the leather-capped Lenin, who was clambering onto a tub of flowers to see over the heads of the crowd. Around him the dancing had stopped and the football went rolling down the steps unheeded.

'Walk that way, through the trees,' I told Munte. 'You'll meet a broad-shouldered man, about my age, wearing a coat with an astrakhan collar. In any case, keep going along the road until you see a very big truck with a bright yellow tarpaulin marked "Underberg". Stop the truck and get in. Your wife will be there already.'

'What about you?'

'I'll try to delay the police.'

'That's dangerous, Bernd.'

'Get going.'

'Thank you, Bernd,' said the old man soberly. We both knew that, after Weimar, it was what I had to do for him.

'Walk, not run,' I called as he ambled away. His dark suit ensured that he would soon be swallowed up by the gloom of the forest.

I pushed my way along to the edge of the lake. A number of men had walked out on the little pier and climbed into a small sailing boat. Now someone was trying to untie the mooring ropes, but it was proving difficult for the maladroit drunk. One of the restaurant staff was shouting at the men, but they paid no heed.

A very loud cheer brought my attention round to the beer garden again. Three young drunks were walking along the top of a low wall. Each carried a pitcher of beer and wore a black top hat, and each was otherwise naked. Every few paces they stopped, bowed deeply to acknowledge the applause, and then drank from the jugs.

Lenin had his three cohorts at his side as he elbowed his way through the muttering crowd of holiday makers, their exuberance stifled by his presence. Thinking the policemen were there to check absentees from work, and were about to arrest the streakers, the onlookers were resentful. Intoxication emboldened them enough to show their resentment. There were catcalls. The four policemen were jostled and pushed. They were confronted by a particularly big opponent, a bearded man in sweat shirt and jeans, who seemed determined to bar their way. But they were trained to deal with such situations. Like all cops, they knew that quick action, with a nicely judged degree of violence, is what crowd control depends upon. One of the uniformed cops felled the bearded man with a blow of his truncheon. Lenin blew three blasts on his whistle – to suggest that many more policemen were on call – and they plunged on through a crowd which parted to make way for them.

By now Munte was a hundred yards or more into the forest and out of sight, but Lenin had obviously spotted him for, once through the thickest part of the crush of men, he began running.

I ran, too, choosing a path that would converge on the policemen's. I ran alongside them through the springy undergrowth of the dark forest. Lenin looked round to see who was chasing him, saw me, and looked to his front again. 'This way!' I shouted, and headed down a path that led back to the lakeside.

For a moment Lenin and his three subordinates continued going the way that Munte had gone. Surely the old man had heard them coming after him by now. 'You four!' I shouted with the sort of arrogance that was calculated to convince them of my seniority. 'This way, you bloody fools. He's heading for the boat!'

Still the men raced after Lenin, while I continued on the path. This was my last chance. 'Do you hear me, you idiots?' I shouted breathlessly. 'This way, I say!'

My desperation must have been the convincing factor, for Lenin changed direction and came thumping across the forest floor, his ammunition boots shaking the earth, his eyeballs dilated and his face bright red with exertion. 'The boat is hidden,' I shouted to account for what I guessed would be the complete absence of any boat when they reached the water. I waved the uniformed cops past me and then went back up the path as if expecting more policemen who might need guidance.

But by the time I was fifty yards up the track, Lenin had got to the waterfront and found no boats or places along the lake's edge where any could be hidden. He'd sent the young Saxon conscript back to find me.

'Stop, sir,' said the cop in that unmistakable accent.

'This way!' I shouted, bluffing to the end.

'Stop, sir,' said the cop again. 'Stop or I shoot.' He had his pistol in his hand. I reasoned that a conscript lad who argued with the leader of his arrest team might well be the type who would pull the trigger. I stopped. 'Your identification, please, sir,' said the cop.

I could see Lenin plodding back up the path, breathing heavily and wriggling his fingers in anger. The game was up. 'I was just trying to help,' I said. 'I saw him come this way.'

'Search him,' said Lenin to the Saxon boy. He paused to catch his breath. Then take him back and lock him up.' To the other cop he said, 'We'll go to the Müggelheimer Damm, but we've probably lost them. They must have had a car waiting there.' He came very close to me and stared me in the eyes. 'We'll find out all about it from this one.'