Standing there is a stranger holding a large book, who says "Marcus Rowland?"
"I'm Frank Jacobs, and I've brought you a copy of my book!"
The book is Strange Maps, An Atlas of Cartographic Curiosities (UK details here), and he's apparently touring and leaving copies with people who contributed material - my bit was from an article called What The World May Come To, which proves that one day the Earth will be a tetrahedron.
To say that I was surprised is putting it mildly - I couldn't even get him to come in for coffee, and by the time I thought of giving him a copy of my collected works he was long gone. I'll have to post him some stuff instead...
Anyway, his web site is here and there's a livejournal feed as strangemaps which I thoroughly recommend. And the book is REALLY nice!