Even the serious drinkers were quiet. A group near the bar were speaking in that stilted German that is usually the sign of the expatriate. One said, 'I don't know why people say the Austrians are venal, it took them more than a century to discover how much money they could make out of Mozart.'

His companion shushed him. Rightly so, for even his quiet voice was audible on the other side of the hotel. Then suddenly there was a loud shuffling and squeaking noise from the revolving doors and into the lobby there came two young couples. They had gleaming complexions and perfect wavy hair. Their clothes were chic and expensive and the women wore glittering jewellery and they all had that boisterous self-confidence with which the wealthy are so often endowed. They were not stamp dealers. Everyone turned to see them, for their sudden entrance into the sombre hotel lobby was unwelcome, like noisy brightly coloured TV advertisements interrupting the soft nostalgia of an old black and white film.

They must have sensed the feelings their unexpected appearance had provoked, for they became quieter and their movements more composed as they made their way across the marble floor. The lift was not working, so they went up the grand staircase to their rooms. The eyes of every man followed the progress of the glamorous people, the women with their long dresses decorously lifted as they ascended the stairs, the young men murmuring together.

I looked around for the mysterious American but there was no sign of him. I had done enough for one day: I went to bed. As I put my head on the pillow a clock began to chime eleven and soon another one joined in.

The auction started exactly on time, as most things do in that part of the world. It was all Zeppelin mail today, starting with the earliest examples, mail of the 'pioneer' airships Viktoria Luise and Schwaben. Then came one postcard from the airship Deutschland which bore the airship company's red stamp, and the bidding just kept going and going until it reached the sky. There were three men after the card and the room went silent as the auctioneer just kept his litany of numbers going with glances from one side to the other. The bidding stopped suddenly as two of the men seemed to decide simultaneously that there was no longer a margin of profit left. Crack, went the hammer, and the reaction was a sudden shuffle of tense muscles and released breaths. They were all writing the price into their catalogues. This would set a higher value for such items and would mean a reappraisal of their stocks.

The room wasn't crowded but there was a continuous flow of people as specialists interested in particular items came in and took part in some spirited bidding and then went to drink coffee in the glassed-in sidewalk café, or out on the terrace to smoke and chat with their colleagues.

They must have been running a bit behind time that morning, for the auctioneer kept glancing at his watch and there seemed to be a general tendency to hurry things along.

As the auction reached 1914, and the wartime Zeppelins, there was something of an exodus that left only a couple of dozen specialists. Whether this was because the First World War items were a neglected part of the stamp collector's world, or because this particular auction contained poor examples, I had no way of knowing. But when the auctioneer announced the beginning of a Hungarian collection of Graf Zeppelin mail, sold by order of the executor of the deceased man's estate, almost every chair was taken, and there were some who preferred to remain standing at the very back.

I was ready well before Lot 584 was offered for sale. Face down on the table in front of me there was a large white card printed with a big black number 12. That was my number and when the bidding for 584 began I tipped it up so that it was visible to the auctioneer. For a fraction of a second he met my eyes to tell me that I was in the auction, and increased the bid accordingly. Behind me there must have been a dozen or more bids offered somewhat mechanically. The price kept going up, and it was hard to know whether my raised card made any difference. The auctioneer looked into the distance and deliberately gave no clue as to where the bids were coming from.

The bidding slowed. That first flurry of bids had gone, leaving more serious ones. 'One thousand nine hundred!' he called, and as the total increased each bid was a bigger jump. Suddenly we were into bigger bids. I tipped the card to keep the bidding going but someone behind me was interested too. We were now at double the estimated price and the bids were still coming!

The auctioneer didn't look surprised. That morning there had been other things to surprise him more: items ignored and items fetching three or four times their estimates. I tried to remember how much cash I had in my wallet over and above the money that Hoffmann had left with me. Two thousand five hundred!' They were 100-schilling increments now, and still going.

'Two thousand six hundred!' Behind me there were two other people bidding for the damned envelope. I turned but could not see either of my rivals.

'Two thousand nine hundred!' The auctioneer was looking at me now, an eyebrow lifted. I showed my bidding card again and he lifted his eyes to somewhere at the back of the room.

'Three thousand…' and even before he said it he was looking over my head and saying 'Three one… Three two…'

His eyes came back to me. I held the card resolutely upright and his eyes passed discreetly over me and to the room. 'Three three… three four… three five…'He hadn't even brought his eyes back to me. There must be two of them fighting it out. And they weren't slowing. I turned to see the room. One of the auction officials was standing in the corner at a telephone. He lifted his hand. So it was a phone-in customer who was bidding against me plus someone at the back of the room.

'Three thousand seven hundred schillings!'

Some sort of pause had come in the bidding, for the auctioneer's eyes came back to me. 'Three thousand seven hundred schillings at the back of the room,' he said.

I nodded. The auctioneer said, Three eight at the front of the room.'

From somewhere behind me I heard a German voice say, Three nine,' and then another German voice say, Tour thousand on the phone.'

'Four thousand one hundred at the back of the room,' said the auctioneer. And then immediately, 'Four two…three…four, five.' Even the auctioneer was surprised. 'Four thousand six hundred at the back of the room.'

He was looking at me. I nodded. He looked up and said, 'Four…' and then said, 'Five thousand one hundred schillings to the back of the room.'

I turned to get a proper look at who was bidding and was in time to see the man at the telephone wave a hand to indicate the bidder had stopped.

'For the second time: five thousand one hundred schillings,' said the auctioneer looking at me quizzically.

I lifted the numbered card. 'Five two at the front.'

For a moment I thought the bidding had stopped. I was relieved. If I turned out all my pockets and persuaded the hotel to take an English cheque I might put together that amount of cash. Then the auctioneer said, 'Five three…'and then without looking in my direction at all he said, 'Five four… Five five.'

Someone else had joined the bidding and before I could catch my breath the price was at six thousand Austrian schillings.

The auctioneer was tapping his hammer again. 'For the third time…' I shook my head. 'Gone!'

Once again the Department had given their orders and then so arranged things that the man in the field could not carry them through. I put the numbered card in my pocket as a souvenir and got to my feet. I wanted to see the man who now owned what I'd been sent here to buy.