'Ahh! You're just covering your arse,' said Werner. 'You don't really think there's another KGB source in London Central, but you realized that you'd have to interpret it that way in case anyone thought it was you and you were trying to protect yourself.'

'Don't be stupid.'

'I'm not stupid, Bernard. I know London Central and I know you. You're just running round shouting fire in case someone accuses you of arson.'

I shook my head to say no, but I was wondering if perhaps he was right. He knew me better than anyone, better even than Fiona knew me.

'Are you really going to hang on until they get that motor car out of the water?'

That's what I'm going to do.'

'Come back for a bite of dinner. Ask the police inspector to phone us when they start work again.'

'I mustn't, Werner. I promised Lisl I'd have dinner with her at the hotel in the unlikely event of my getting away from here in time.'

'Shall I phone her to say you won't make it?'

I looked at my watch. 'Yes, please, Werner. She's having some cronies in to eat there – old Mr Koch and those people she buys wine from – and they'll get fidgety if she delays dinner for me.'

'I'll phone her. I took her a present yesterday, but I'll phone to say Happy Christmas.' He pulled the collar of his coat up and tucked his white silk scarf into it. 'Damned cold out here on the river.'

'Get back to Zena,' I told him.

'If you're sure you're not coming… Shall I bring you something to eat?'

'Stop being a Jewish mother, Werner. There are plenty of places where I can get something. In fact, I'll walk back to your car with you. There's a bar open on the corner. I'll get myself sausage and beer.'

It was nearly ten o'clock at night when they dragged the ambulance out of the Havel. It was a sorry sight, its side caked with oily mud where it had rested on the bottom of the river. One tyre was torn off and some of the bodywork ripped open where it had collided with the railings that were there to prevent such accidents.

There was a muffled cheer as the car came to rest. But there was no delay in finishing the job. Even while the frogmen were still packing their gear away, the car's doors had been levered open and a search was being made of its interior.

There was no body inside – that was obvious within the first two or three minutes – but we continued to search through the car in search of other evidence.

By eleven-fifteen the police inspector declared the preliminary forensic examination complete. Although they'd put a number of oddments into clear-plastic evidence bags, nothing had been discovered that was likely to throw any light on the disappearance of Carol Elvira Miller, self-confessed Russian agent.

We were all very dirty. I went with the policemen into the toilet facilities at the wharfside. There was no hot water from the tap, and only one bar of soap. One of the policemen came back with a large pail of boiling water. The rest of them stood aside so that the inspector could wash first. He indicated that I should use the other sink.

'What do you make of it?' said the inspector as he rationed out a measure of the hot water into each of the sinks.

'Where would a body turn up?' I asked.

' Spandau locks, that's where we fish them out,' he said without hesitation. 'But there was no one in that car when it went into the water.' He took off his jacket and shirt so that he could wash his arms where mud had dribbled up his sleeve.

'You think not?' I stood alongside him and took the soap he offered.

'The front doors were locked, and the back door of the ambulance was locked too. Not many people getting out of a car underwater remember to lock the doors before swimming away.' He passed me some paper towels.

'It went into the water empty?'

'So you don't want to talk about it. Very well.'

'No, you're right,' I said. 'It's probably just a stunt. How did you get the information about where to find it?'

'I looked at the docket. An anonymous phone call from a passerby. You think it was a phony?'

'Probably.'

'While the prisoner was taken away somewhere else.'

'It would be a way of getting our attention.'

'And spoiling my Christmas Eve,' he said. 'I'll kill the bastards if I ever get hold of them.'

'Them?'

'At least two people. It wasn't in gear, you notice, it was in neutral. So they must have pushed it in. That needs two people; one to push and one to steer.'

'Three of them, according to what we heard.'

He nodded. 'There's too much crime on television,' said the police inspector. He signalled to the policeman to get another bucket of water for the rest of them to wash with. 'That old English colonel with the kids' football team… he was your father, wasn't he?'

'Yes,' I said.

'I realized that afterwards. I could have bitten my tongue off. No offence. Everyone liked the old man.'

'That's okay,' I said.

'He didn't even enjoy the football. He just did it for the German kids; there wasn't much for them in those days. He probably hated every minute of those games. At the time we didn't see that; we wondered why he took so much trouble about the football when he couldn't even kick the ball straight. He organized lots of things for the kids, didn't he. And he sent you to the neighbourhood school instead of to that fancy school where the other British children went. He must have been an unusual man, your father.'

Washing my hands and arms and face had only got rid of the most obvious dirt. My trench coat was soaked and my shoes squelched. The mud along the banks of the Havel at that point is polluted with a century of industrial waste and effluents. Even my newly washed hands still bore the stench of the riverbed.

The hotel was dark when I let myself in by means of the key that certain privileged guests were permitted to borrow. Lisl Hennig's hotel had once been her grand home, and her parents' home before that. It was just off Kantstrasse, a heavy grey stone building of the sort that abounds in Berlin. The ground floor was an optician's shop and its bright facade partly hid the pockmarked stone that was the result of Red Army artillery fire in 1945. My very earliest memories were of Lisl's house – it was not easy to think of it as a hotel – for I came here as a baby when my father was with the British Army. I'd known the patched brown carpet that led up the grand staircase when it had been bright red.

At the top of the stairs there was the large salon and the bar. It was gloomy. The only illumination came from a tiny Christmas tree positioned on the bar counter. Tiny green and red bulbs flashed on and off in a melancholy attempt to be festive. Intermittent light fell upon the framed photos that covered every wall. Here were some of Berlin 's most illustrious residents, from Einstein to Nabokov, Garbo to Dietrich, Max Schmeling to Grand Admiral Donitz, celebrities of a Berlin now gone for ever.

I looked into the breakfast room; it was empty. The bentwood chairs had been put up on the tables so that the floor could be swept. The cruets and cutlery and a tall stack of white plates were ready on the table near the serving hatch. There was no sign of life anywhere. There wasn't even the smell of cooking that usually crept up through the house at night-time.

I tiptoed across the salon to the back stairs. My room was at the top – I always liked to occupy the little garret room that had been my bedroom as a child. But before reaching the stairs I passed the door of Lisl's room. A strip of light along the door confirmed that she was there.

'Who is it?' she called anxiously. 'Who's there?'

'It's Bernd,' I said.

'Come in, you wretched boy.' Her shout was loud enough to wake everyone in the building.

She was propped up in bed; there must have been a dozen lace-edged pillows behind her. She had a scarf tied round her head, and on the side table there was a bottle of sherry and a glass. All over the bed there were newspapers; some of them had come to pieces so that pages had drifted across the room as far as the fireplace.