He made no attempt to avoid detection. He looked sixtyish; wavy hair, a bit overweight but physically rather trim. He was wearing a Black Watch tartan jacket and dark slacks with a spotted bow tie. His neatly trimmed grey beard and gold-rimmed bifocals all added up to an American college professor on a sabbatical. He was leaning against the edge of a table and as he saw me he smiled and edged his way past the other men to join me. I waited for him.

'Oh boy! I wondered what was happening,' he said in English with a soft American accent. 'I thought you maybe had a buy bid too.'

'No, 'I said. 'I had a limit.'

'And am I glad you did. We could have gone through the ceiling. Can I buy you a drink?'

'Thanks,' I said.

'I haven't seen you around before.'

'I work in London,' I said.

As we reached the door he asked one of the auction staff where he could pick up his purchase and was told to go to the cashier's office – a room on the ground floor at the back of the hotel. It was all well-organized, and evident that the same firm held auctions here regularly.

'Jesus, look at that rain and it's becoming hail,' he said as we walked past the bookstall and along the corridor.

There was a line waiting outside the cashier's office when we got there. We joined the line. 'It was a good item but I've seen better,' said the man, continuing with the conversation. 'My name is Johnson, Bart Johnson. I work in Frankfurt but I come from Chicago. Are you a Zeppelinpost expert?'

'No,' I said.

He looked at me and nodded. 'Well Graf Zeppelin is a kind of hero for me. I was always crazy about airships. It started when I was a kid and someone gave me a piece of fabric from the Shenandoah that crashed in Ohio in 1925. I've still got it, framed on the wall. Yes, back in my office I keep a file on everything. And I looked up Berezowski's Handbuch der Luftpostkunde… You know that of course?'

'I'm not sure I do.'

'Jesus, I depend on Berezowski even more than I rely on the Sieger Katalog.' In his hands he had a catalogue and a blue folder containing cuttings and handwritten notes. He flipped it open to refer to it.

I sensed that some reaction was expected so I said, 'Do you really?'

'Berezowski's 1930 book is a classic for this kind of reference. It's been reprinted: you can still buy copies. I'll give you an address and you can get one mailed. But in the clippings I came across an article that Dr Max Kronstein wrote in the Airpost Journal in January 1970. He says the Paraguay post office refused to accept International Reply Coupons; that's why Paraguay mail is so rare. The only mail with Paraguay adhesives came from residents – foreign residents.'

'That's very interesting,' I said.

'Yes, isn't it?' He flipped the file closed and put a gold pencil into his pocket. 'And ever since Sieger listed the mail to Europe as being worth ten per cent more than mail to USA, our customers prefer it. In fact I looked up Kummer: he says that only sixty items went to the USA and about 180 to Europe so I'd say it was the other way around. Mind you, you can never be sure because mail sent to Europe might have been destroyed by the war, while items in American collections remained safe.' He kept a finger in the file, as if it might be necessary for him to prove these contentions to me by references to it.

'Yes,' I said.

'Sure. I know. I mustn't go on so much. You seem kind of disappointed. Was it for your own collection?'

'No, it was just a job.'

'Well, don't take it to heart, fella. There's a whole lot more Zeppelinpost out there waiting to be bought. Right?' I nodded, He stroked his beard and smiled. The line moved forwards as some dealers emerged from the office with their purchases.

'Say, who was that character I saw you talking with on the terrace yesterday?'

'An acquaintance,' I said.

'What's his name?'

'I've been trying to remember,' I said. 'I thought he was with you.'

'Thurkettle,' he supplied. 'He said his name was Ronnie Thurkettle. So he's not a buddy of yours?'

'I hardly know him.' Now I remembered the name but his face was still not familiar to me.

'Say, what kind of work does that guy do? He's not in the stamp business is he? I used to see him in Frankfurt and all around but I never figured what kind of job he has.'

'Works for the State Department,' I said. 'But that's all I know about him.'

'He buttonholed me yesterday. He came on real friendly, but he just wanted to pick my brains about Zeppelinpost. He doesn't know the first thing about airmail. He was expecting me to explain the catalogue to him. I told him to go and get a good book on the subject. I'm not about to give lessons to guys like him: he's not my kind. Know what I mean?'

'How did he take it?'

'Take it? He backed off and changed the subject. He's not a friend of mine. No way. I just used to see him around when I was in public relations. Frankfurt; I'd see him at those little shindigs the contractors give to entertain visitors: cute little weenies on a stick and diluted Martinis. You know. I guessed he was with the government. Washington is printed all over him: right? But I thought maybe he was a civilian with the army.'

'No,' I said. 'State.'

'I stay well away from those guys. They bring trouble and I don't need it.' The line moved again until we were at the front. A soft buzzer sounded and the security man signalled for us to go in. There was not much room in the cashier's office. A morose clerk looked through a small metal grille. Behind him there was a girl with a table piled with philatelic covers and cards in transparent plastic and a cash box full of cheques and money of all denominations. 'Johnson's the name. Johnson, Bartholomew H.,' said my companion. ' Lot 584. Six thousand schillings. I have an account with you.' The room had an unfamiliar smell, like incense. Maybe it was the clerk's after-shave. Or the money.

The man behind the grille turned the pages of the book. 'What number?' he asked.

' Lot 584.' Johnson now had a thick bundle of Austrian money in his hand. He riffled it. It seemed as though all these stamp dealers liked cash.

'There must be a mistake,' said the man behind the grille.

'Johnson Bartholomew H. I have an account. Six thousand schillings. If you want cash, I have it here.' He flip-flopped the wad of money and said, I'm not going to spend ten thousand schillings before getting on the plane this afternoon.'

The clerk said, ' Lot 584 went for six thousand two hundred schillings. A telephone bid.'

'No sir!' said Johnson. 'I got it.'

'You have made a mistake, sir,' said the man behind the grille.

'You've made the mistake, buddy. Now give me my cover.'

'I'm sorry.'

'I insist. It's mine! Now let me have it.' He was angry.

'I'm afraid it's no longer here,' said the clerk. 'It went off with a lot of other material. It's for a very well-known client.'

'What am I?' said Johnson angrily.

'I'm sorry you are disappointed, sir,' he said. 'But there is really nothing I can do and there are many other customers waiting.'

'How do you like that?' He shouted so loudly that the security man looked around the door, but the steam was going out of him.

'Let's get out of here,' I said, a number one rule amongst the people I work with being never get tangled with the law.

'You haven't heard the last of this!' Johnson said to the man behind the grille.

I'm very sorry, sir. I really am.'

Once out in the corridor again we both became objects of curiosity for those who had heard Johnson shouting. He brushed the front of his suit self-consciously and said, 'Come on. Let's get a drink.'

'Good idea,' I said.

It took him several minutes to recover his composure. He seemed really rattled. If it was all an act it was an Oscar-worthy performance. Once seated at the counter in the bar he said, 'What the hell was that all about? You were there. You saw me get that damned cover. Or am I going nuts?'