'With what?'

'It's nice to see you again, Bernd. But you work out of London nowadays, you say. With only a couple of days in the city and lots of old friends to visit, you didn't come to my little place to talk about how well I did in my chemistry exams, and have a can of beer – which I notice you drink very very slowly, as policemen do when they are on duty – and be interrupted by the shouting of the kids next door, and sit close to the heating because I can't afford to turn it up any higher. You must have had a reason to come here, and I think you are going to ask me a favour.'

'Remember a couple of years ago when I was looking for that kid who'd stolen a briefcase from an office near the Zoo station?'

'You asked me to look up a post-office box number and tell you who rented it. But that was an official request. That came through the British Army.'

'This one is more delicate, Axel.' I took from my pocket the envelope that Frank Harrington had left in my street guide. Axel took it reluctantly; even then he didn't immediately look at it. 'It's urgent, I suppose? These things are always urgent.' He read the address.

'It is, Axel. Otherwise I could have gone through the post office.'

He laughed scornfully. 'Have you tried getting anything out of our wonderful post office lately? Last week it took them four days to deliver a letter from a postbox in Tiergarten, and then it was nearly torn in two. And the price for a letter now…'He read the numbers that were the address. 'One thousand is Berlin and twenty-eight is Lübars.'

'You said Polizeipräsidium kept copies of the forms the box renters sign. Could you get the name and address of the person who rents that box at Lubars post office? Could you get it even on a Saturday?'

'I'll phone from the bedroom.'

Thanks, Axel.'

'It depends who's on duty this morning. I can't order anyone to do it. It's strictly forbidden… it's a criminal offence.'

'If I could clear up the inquiry immediately, I could go home.'

'We all thought you'd grow up to become a gangster,' said Axel. 'Did I ever tell you that?'

'Yes, Axel. You've told me that many times.'

'We asked Herrn Storch, the mathematics teacher, but he said all the English were like you.'

'Some of them are worse, Axel,' I said.

He didn't laugh; he nodded. He wanted me to know how much he disliked it. He wanted me to think twice before I asked him more such favours. When he went into the bedroom to phone, he turned the key in the door. He wanted to be sure that I could not get close enough to hear him.

The call took only five minutes. I suppose the Polizeipräsidium have such records on a computer.

'The addressee, Mrs Harrington, is the renter of the box. She gave no an address in Lübars,' said Axel when he returned from the phone. 'I know exactly where it is. It's a street of beautiful houses with a view across open farmland. What wouldn't I give to live in such a place.'

'How difficult is it to get a postbox in a false name?' I asked.

'It depends who is on duty. But you don't have to provide much to get it in any name you wish. Many people have boxes under a nom de plume or a stage name, and so on.'

'I have not been to Lübars since we were kids. Is it still as pretty as it used to be?'

'Lübars village. We're quite close. If this window faced north, I could show you the street. They've preserved everything: the little eighteenth-century village church, the fire station and the village green with the fine chestnut trees. The farmhouses and the old inn. It's just a stone's throw away but it's like another world.'

'I'll get going, Axel,' I said. 'Thanks for the beer.'

'And what if on Monday they fire me? What then? You say how really sorry you are, and I spend the rest of my life trying to support a family on social welfare payments.'

I said nothing.

'You're irresponsible, Bernd. You always were.'

I would have expected Frank Harrington to have his mistress hidden away in a small anonymous apartment block somewhere in the French Sector of the city where no one notices what's happening. But the address Axel Mauser had provided was in the northernmost part of the Western Sector, a prong of land sandwiched between the Tegel Forest and the Wall. There were small farms here just a short way from the city centre, and tractors were parked on the narrow cobbled lanes among the shiny Porsches and four-litre Mercedes.

The big family houses were designed to look as though they'd been here since Bismarck, but they were too flawless to be anything but reconstructions. I cruised slowly down an elegant tree-lined road following three children on well-groomed ponies. It was neat and tidy and characterless, like those Hollywood back lots designed to look like anywhere old and foreign.

Number 40 was a narrow two-storey house, with a front garden big enough for two large trees and with a lot of empty space behind it. There was a sign on the chain fence, bellevue kennels, and another that said beware of the dogs in three languages, including German. Even before I'd read it, the dogs began barking. They sounded like very big dogs.

Once through the inner gate, I could see a wired compound and a brick outbuilding where some dogs were crowding at the gate trying to get out. 'Good dog,' I said, but I don't think they heard me.

A young woman came from somewhere at the back of the house. She was about twenty-two years old, with soft grey eyes, a tanned sort of complexion, and jet-black hair drawn back into a bun. She was wearing khaki-coloured cotton pants, and a matching shirt with shoulder tabs and button-down pockets. It was all tailored to fit very tight. Over it she had a sleeveless sheepskin jacket – fleece inwards – with the sort of bright flower-patterned embroidery that used to be a status symbol for hippies.

She looked me up and down long enough to recognize my Burberry trench coat and Professor Higgins hat. 'Did you come to buy a dog?' she said in good English.

'Yes,' I said immediately.

'We only have German shepherds.'

'I like German shepherds.' A big specimen of this breed emerged from the house. It came within six feet of us, looked at the woman, before hunching its shoulders and growling menacingly at me.

'You didn't come to buy a dog,' she said, looking at my face. Whatever she saw there amused her, for she smiled to show perfect white teeth. So did the dog.

'I'm a friend of Frank's,' I said.

'Of my Frank?'

'There's only one Frank,' I said. She smiled as if that were a joke.

'Has anything -?'

'No, Frank is fine,' I said. 'In fact, he doesn't even know I've come to see you.'

She'd been peering at me with eyes half closed, and now suddenly she opened her mouth and gave a soft shout of surprise. 'You're Werner's English friend, aren't you?'

We looked at each other, momentarily silenced by our mutual surprise. 'Yes, I am, Mrs Volkmann,' I said. 'But I didn't come here to talk about Werner.'

She looked around to see if her neighbours were in their garden listening. But her neighbours were all safely behind their double-glazing. 'I can't remember your name but you are the Englishman who went to school with Werner… Your German is perfect,' she said, and changed into that language. 'No need for us to speak English. I'll put Rudolf in the run and then we'll go inside and have coffee. It's made already.' Rudolf growled. He did not want to go into the run unless he took me with him.

'During the week, I have a girl to help me,' said Mrs Zena Volkmann while Rudolf submitted meekly to being pushed into the wired compound. 'But at the weekend it is impossible to get anyone at any price. They say there is unemployment but people just don't want to work, that's the trouble.' Now her accent was more distinct. Ostelbisch: Germans from anywhere east of the River Elbe. Everyone agrees it is not pejorative, but I never heard anyone say it except people who came from west of the River Elbe.