'My fate was sealed. I was an international currency smuggler'. Andrew Hasson remembers 1980 in Berlin
Sitting in the interrogation room, I tried to work out if I had made a profit or a loss. Two very angry border guards had just walked out of the room, slamming the door behind them. I noticed there was no door handle on the inside.

After an hour or so, they'returned, glaring hard. They were accompanied by someone who looked like a member of the women's shot-putt team: their superior officer. She looked me up and down in disgust and told me I had committed a grave offence against the state.

It was the summer of 1980. A levels were over and Fred and I had failed to secure jobs, much to our parents' dismay. We had a friend in Berlin; maybe we could stay with him and find some work for the summer?

Coming from Sussex, we weren't used to 24-hour bars, or policemen tooled up with sub-machine guns. We'd never seen a one-legged prostitute before, nor a pensioner shooting up heroin at 6.30 in the morning. We were the archetypal innocents abroad, and neither of us had been arrested before. I got there first.

I landed a job at Tegel Airport loading bags on to the planes. My German came on in leaps and bounds. I was hungry to see everything the city had to offer so a day over the border in East Berlin was planned.

The "official" exchange rate (the DDR rate) gave one Deutschmark for one East Mark. It bore no relation to reality. Travelling from from West to East for the day required compulsorily exchanging 25 Deutschmarks for 25 aluminium, lighter-than-air East Marks. There was only one place the East Germans would allow you to buy East Marks and that was at the border.

Nonetheless, every bank in West Berlin exchanged D-Marks at the "proper" rate of five for one East Mark and there was nothing the Democratic Republic could do about it. Of course, nobody at the bank told you that taking this money over the border could land you in deep trouble. There was no need, because everyone knew it anyway. Once in the east, you were rich.

The downside was that in East Berlin there was nothing to spend it on. There were no record shops and the clothes were shoddy; the average teenager could die waiting to spend money over here. Rather pompously, after drinks and a sandwich in a bar, I thought giving out a big tip to these poor suppressed communists would change the world. I spent the day wandering around, attempting to take in all the weirdness.

I had unofficially exchanged DM20, which was worth pounds 5 in those days, giving me 100 East Marks; an illusion of wealth I had never previously experienced. Add this to the officially-exchanged 25 Marks, and I had far too much, so I looked around for something to buy. I found a calligraphy set (which I knew I would never use) for 50 Marks and I headed back to the Friedrichstrasse border crossing (also known as Checkpoint Charlie).

In the customs room, I was pulled aside; "Where did you get the money for this?" asked the officer, pointing at the useless calligraphy set, which had clearly cost more than 25 Marks. I feigned ignorance of the German language. "Sorry, I'm a tourist," I smiled back.

Twenty long minutes later an interpreter arrived and ordered me into a room to give a statement. Still I didn't worry. I proceeded to answer their questions. I was a tourist, I told them. I'd gone into a West German bank asking for East German currency. What was wrong with that?

"It's illegal," said the interpreter, so I expressed surprise. "Why do they do it then?"

I was questioned about my movements that day. At one point, my interpreter mistranslated some trivial detail of my statement and I corrected him. They stopped and turned to look at me with narrowing eyes. "You do speak German!" they shouted together.

"Well, just sort of. Tourist German," I offered feebly.

"Rubbish," screamed the interpreter, looming over me like a giant Communist- style heroic statue. "You don't play games with the DDR! Where do you really live?"

"Just down the road. In the West," I snivelled. My fate sealed. I was an international currency smuggler.

The fine, in West Marks, was announced as DM400 (the equivalent of pounds 100). Two weeks later, I went down to Checkpoint Charlie to pay. In the intervening weeks, I'd dislocated my knee-cap and the hospital had encased my entire leg in plaster. The shot-putt officer was there, hardly believing I'd come back to pay the fine (looking back, I can hardly believe it myself). I told her I'd broken my leg and lost my job so I had only half the money. She took it and ordered me back the following month.

I didn't go and, in less than a decade, the DDR was gone. My entry in their books probably still shows me to be 200 marks in the red.