Justus seemed to have decided that I needed looking after. He'd come over during the conference coffee break, told me how much he'd enjoyed my paper, explained that he was a postgraduate sociologist at Amsterdam University, and then asked if we could talk a little about his thesis while he showed me his home town. "What are you fancying first?" he asked as we set off down a narrow street beside the Krasnapolsky. "Beer, joint, or quick sex show?"

"Not a sex show." "Why not?" I explained that after a long day talking about Amsterdam becoming a creative city, it seemed anachronistic to opt for such a traditional urban pleasure. "It is not traditional. They do it on stage. Not miming. Real sex. People get really fucked." "So I've heard. But not now. Some other time."

"How about a joint, then?" Yes, I said, I'd be only too happy to have a joint. But the trouble was that I'd recently stopped smoking and couldn't risk the tobacco. "It is looking like a beer then."

Half way through the first round of white beers, Justus disappeared for five minutes and came back with a small paper bag. "You are not smoking so you can have this." He took out two large soft biscuits and pushed one in my direction. "Space cake," he explained, tucking in. There was nothing else to be done. I matched him bite for bite.

It took me fifteen minutes to realise my mistake. I'm as familiar as seventy–five per cent of the UK adult population with the squiffy disorienting effects of a casual spliff, but this was an utterly new dimension. It was as though a knife had sliced through my cortex and completely severed the usual connections between my sensory and motor muscles. I could consider moving, go through the mental process that normally preceded movement, but there was no sign whatsoever that my musculature was paying a scrap of attention. I'd think about moving my foot. Decide to move it. Then look down and find that it was still completely immobile.

Justus was displaying no such symptoms. He was busily asking me what I really thought about Richard Florida's famous three T's. Could any city be successful if it had technology, talent and tolerance?

All I could do was mentally command my face to adopt a thoughtful look. I certainly couldn't speak and I had no real way of knowing whether my facial muscles were producing any sort of recognisable expression. I certainly had no time at all to think about the creative city. I had to reserve every brain cell left at my disposal for the inordinately complex task of picking up my glass, carrying it to my lips, and taking a sip of beer.

Now he was talking about the nature of tolerance, talking about how tolerance in Holland was a product of the waterworks. About how you couldn't have an authoritarian society if you had to look after the dykes. I tried again to twist my face into a shape that might suggest some sort of comprehension. And then a breakthrough. If I tried very hard, I found that I could emit something that was recognisable as a grunt. Uh, uh, I went. Uh, uh.

What felt like several days and nights passed by and still Justus talked. Now he was talking about front doors and back doors in Amsterdam. About how dope was legal at the front and illegal at the back. Or the other way round. Uh, uh.

Finally, he stopped. It was my turn to say something. Anything. I struggled to get my mouth into gear. "Ith's been great thorking to you," I stammered. "And you," he said, getting up smoothly from his seat and reaching for his coat. "See you at the conference tomorrow." "Yeth indeed." Two hours later I twisted my brain and legs into some sort of temporary alignment and staggered home to bed.

Last Thursday a Sunflowers postcard arrived. "Dear Lorry. It was very good to have such talking in Amsterdam. Most of my professors always seem too busy to listen. You are making a change. Thank you for all your helpful commenting. Yours. Justus."

"Dear Justus," I wrote on the back of Whistler's Chelsea Bridge, "It was good to listen to your ideas. Good luck with your thesis. It sounds fascinating." I decided it might be unnecessarily cryptic if I added a PS thanking him for letting me discover the true meaning of getting really fucked.