Right.

So it's February of 1985, and it's a Chinese restaurant in London, and it's the author's first interview. His publicist had been pleasantly surprised that anyone would want to talk to him (the author has just written a funny fantasy book called The Colour of Magic), but she's set up this lunch with a young journalist anyway. The author, a former journalist, has a hat, but it's a small, black leathery cap, not a Proper Author Hat. Not yet. The journalist has a hat too. It's a greyish thing, sort of like the ones Humphrey Bogart wears in movies, only when the journalist wears it he doesn't look like Humphrey Bogart: he looks like someone wearing a grown-up's hat. The journalist is slowly discovering that, no matter how hard he tries, he cannot become a hat person: it's not just that it itches and blows off at inconvenient moments, it's that he forgets, and leaves it in restaurants, and is now getting very used to knocking on the doors of restaurants about 11:00am and asking if they found a hat. One day, very soon now, the journalist will stop bothering with hats, and decide to buy a black leather jacket instead.

So they have lunch, and the interview gets printed in "Space Voyager" magazine, along with a photo of the author browsing the shelves in Forbidden Planet, and most importantly, they make each other laugh, and like the way the other one thinks.

And the author is Terry Pratchett, and the journalist is me, and it's been two decades since I left a hat in a restaurant, and one and a half decades since Terry discovered his inner bestselling-author-with-a-Proper-Author-Hat.

We don't see each other much these days, what with living on different continents, and, when we're on each other's continents, spending all our time signing books for other people. The last time we ate together was at a Sushi counter in Minneapolis, after a signing. It was an all-you-can-eat night, where they put your sushi on little boats and floated it over to you. After a while, obviously feeling we were taking unfair advantage of the whole all-you-can-eat thing, the sushi chef gave up on the putting sushi on little boats, produced something that looked like the Leaning Tower of Yellowtail, handed it to us, and announced that he was going home.

Nothing much had changed, except everything.

These are the things I realised back in 1985:

Terry knew a lot. He had the kind of head that people get when they're interested in things, and go and ask questions and listen and read. He knew genre, enough to know the territory, and he knew enough outside genre to be interesting.

He was ferociously intelligent.

He was having fun. Then again, Terry is that rarity, the kind of author who likes writing, not having written, or Being a Writer, but the actual sitting there and making things up in front of a screen. At the time we met, he was still working as a press officer for the South Western Electricity Board. He wrote four hundred words a night, every night: it was the only way for him to keep a real job and still write books. One night, a year later, he finished a novel, with a hundred words still to go, so he put a piece of paper into his typewriter, and wrote a hundred words of the next novel.

(The day he retired, to become a full-time writer, he phoned me up. "It's only been half an hour since I retired, and already I hate those bastards," he said cheerfully.)

This was something else that was obvious in 1985. Terry was a science fiction writer. It was the way his mind worked: the urge to take it all apart, and put it back together in different ways, to see how it all fit together. It was the engine that drove Discworld -- "it's not a -- what if..." or an "if only..." or even an "if this goes on..."; it was the far more subtle and dangerous "If there was really a..., what would that mean? How would it work?"

In the Nicholls-Clute Encyclopedia of Science Fiction, there was an ancient woodcut, of a man pushing his head through the back of the world, past the sky, and seeing the cogs and the wheels and the engines that drove the universe machine. That's what people do in Terry Pratchett books, even if the people doing it are sometimes rats and sometimes small girls. People learn things. They open their heads.

So we discovered we shared a similar sense of humour, and a similar set of cultural referents; we'd read the same obscure books, took pleasure in pointing each other to weird Victorian reference books.

A few years after we met, in 1988, Terry and I wrote a book together. It began as a parody of Richmal Crompton's William books, which we called William the Antichrist, but rapidly outgrew that conceit and became about a number of other things instead, and we called it Good Omens. It was a funny novel about the end of the world and how we're all going to die. Working with Terry I felt like a journeyman working alongside a master-craftsman in some medieval guild. He constructs novels like guildmaster might build a cathedral arch. There is art, of course, but that's the result of building it well. What there is more of is the pleasure taken in constructing something that does what it's meant to do -- to make people read the story, and laugh, and possibly even think.

(This is how we wrote a novel together. I'd write late at night. Terry wrote early in the morning. In the afternoon we'd have very long phone conversations where we'd read each other the best bits we'd written, and talk about stuff that could happen next. The main objective was to make the other one laugh. We posted floppy disks back and forth, because this was before e-mail. There was one night when we tried using a modem to send some text across the country, at 300/75 speeds, directly from computer to computer because if e-mail had been invented back then nobody had told us about it. We managed it too. But the post was faster.)

(No, we won't write a sequel.)

Terry has been writing professionally for a very long time, honing his craft, getting quietly better and better. The biggest problem he faces is the problem of excellence: he makes it look easy. This can be a problem. The public doesn't know where the craft lies. It's wiser to make it look harder than it is, a lesson all jugglers learn.

In the early days the reviewers compared him to the late Douglas Adams, but then Terry went on to write books as enthusiastically as Douglas avoided writing them, and now, if there is any comparison to be made of anything from the formal rules of a Pratchett novel to the sheer prolific fecundity of the man, it might be to P.G. Wodehouse. But mostly newspapers, magazines and critics do not compare him to anyone. He exists in a blind spot, with two strikes against him: he writes funny books, in a world in which funny is synonymous with trivial, and they are fantasies -- or more precisely, they are set on the Discworld, a flat world, which rests on the back of four elephants, who in turn stand on the back of a turtle, heading off through space. It's a location in which Terry Pratchett can write anything, from hard-bitten crime dramas to vampiric political parodies, to children's books. And those children's books have changed things. After all, Terry won the prestigious Carnegie Medal for his pied piper tale The Amazing Maurice and His Educated Rodents, awarded by the librarians of the UK, and the Carnegie is an award that even newspapers have to respect. (Even so, the newspapers had their revenge, cheerfully misunderstanding Terry's acceptance speech and accusing him of bashing J.K. Rowling and J. R. R. Tolkien and fantasy, in a speech about the real magic of fantastic fiction.)

The most recent books have shown Terry in a new mode -- books like Night Watch and A Monstrous Regiment are darker, deeper, more outraged at what people can do to people, while prouder of what people can do for each other. And yes, the books are still funny, but they no longer follow the jokes: now the books follow the story and the people. Satire is a word that is often used to mean that there aren't any people in the fiction, and for that reason I'm uncomfortable calling Terry a satirist. What he is, is A Writer, and there are few enough of those around. There are lots of people who call themselves writers, mind you. But it's not the same thing at all.

In person, Terry is genial, driven, funny. Practical. He likes writing, and he likes writing fiction. That he became a best-selling author is a good thing: it allows him to write as much as he wishes. He's Guest of Honour at the World SF convention -- in many ways the ultimate accolade that the world of speculative fiction can bestow on those who have given it much -- and he'll still be writing, between panels, before breakfast, here and there. He'll probably write as much in a day at Worldcon as most other authors will manage on a quiet day when there aren't any DVDs that haven't been watched and the weather precludes spending time in the garden and the phone's out of order -- and Terry will do this while doing his proper Guest of Honour share of panels and readings and socialising and drinking exotic drinks of an evening.

He wasn't joking about the Banana Daiquiris, although the last time I saw him we drank ice-wine together in his hotel room while we set the world to rights.

I'm delighted that he's Guest of Honour at the Worldcon. He deserves it.