A rainy Thursday night in Sheffield. An observer might have noticed a certain buzz in the air, as huddled knots of disparate people began to gravitate towards the Grosvenor House hotel. My eight year old daughter, Alicia, tugged urgently on my sleeve and said "C’mon Dad - hurry up, he’ll be here soon!".

Who were we waiting for? Only the best selling writer living in Britain today, that’s who ...

There is a common perception of the average Discworld fan as a pimply fourteen year old boy in an anorak. The second iteration of this would have the fan as a slightly plump girl with pale skin and a penchant for lacy black dresses and purple eye shadow. The queue that we were in was a illustration of demographics in action - there were snowy haired octogenarians, middle aged mums and dads, students, an extraordinarily tall youth, a blind girl and her dog, bikers, goths, people in suits and ties, and, at most, one or two anoraks amongst the four hundred strong crowd. Given that it was in fact raining quite heavily outside this can perhaps be forgiven.

We filed into the hall, past the Waterstones table groaning under the weight of multiple copies of the paperback of Jingo, and the newly published hardback of Carpe Jugulem, a Discworld vampire tale tagged as ‘Bloody funny’.

Another brief wait, and then the man himself ambled on stage, removed his trademark black hat, looked faintly embarrassed by the somewhat hyperbolic introduction, and then began to speak.

He kicked off by talking about his forthcoming project - ‘the Science of Discworld’ - in which the wizards of the Unseen University accidentally create a miniature version of a strange ball shaped blue-green planet, and naturally send in Rincewind, a wizard so incompetent that he can’t even spell the word wizard, to watch the evolutionary process in action. Terry has worked with a couple of bone fide biologists and physicists to produce an outsiders guide to science and evolution, that promises to be educational and funny at the same time. He also poked gentle fun at those ‘ascent of man’ diagrams that show the progression from Neanderthal to Homo sapiens by shambling across the stage and saying -

"This is me getting out of bed in the mornings, and you’ll notice that in the pictures they manage to never actually show the man’s willy at any point."

Talking about Carpe Jugulem, he explained the introduction of darker and more complex themes in the Discworld canon by explaining that in amongst all of the comedy you need to have some "tragic relief".

For me personally the most interesting part of his talk was the insights that he gave into the process of writing a Discworld novel. He explained that he uses the railway tunnel method - that is starting from either end and working towards the middle - and that using a word processor allows him far more artistic freedom to work on different parts of a story at the same time. He used the analogy of painter, who does not start in the top left corner of the canvas and paint in a steady progression to the bottom right. Rather, they sketch out the broader picture, make sure everything fits, and then go back to put in the fine detail and flourishes.

The very last stage of writing is when he goes back to put in the cigarettes and sherbet lemons.

Cigarettes are those little bits of expository dialogue at the end of the story that tie up the loose ends and lay the story to rest, named for the final scene in a typical American cop show where the detective would explain the plot for anyone who hadn’t been paying attention. Sherbet lemons refer to the sweet shop that Terry frequented as a lad, whose proprietor would carefully measure out a quarter of sherbet lemons and then throw in an extra one for luck. The Discworld equivalents are the extra jokes and footnotes that Terry puts in after his editor has accepted the manuscript and he is, as he says, "working on my own time".

Terry reassured fans that he will never write the "last" Discworld novel, and that although the frequency might drop from his current book a year, his grandfather lived to the ripe old age of 96, so it looks like we can expect at least another thirty or so installments of the Discworld saga.

Opening the discussion out to questions from the floor, Terry talked about his love of the ‘Tombraider’ games with the improbably large breasted Lara Croft. He excused the wholesale slaughter of endangered species on the grounds that they get in the way of the gorgeous scenery. He then wondered where all of the stuff that you find in these games appears from - "Perhaps there should be a ‘Tombstocker’ game where you run around a large maze filling it with guns, ammo and keys ..."

He also talked about his experiences as a press officer for the nuclear industry, relating the tale of the man who triggered the alarms going into the power station where he worked and was actually too radioactive to be allowed in. On further investigation it turned out that he had been dismantling a luminous control panel from a world war II bomber - safety standards were different in those days, and after all, if you flying a bombing mission over Dresden then a mild dose of radiation was the least of your worries.

He also recalled the time when a train carrying low grade waste had jumped the points in a shunting yard. Under railway regulations this was officially classified as an accident, and because of the cargo it was therefore a ‘nuclear accident’. Terry’s thankless task was to try and quell the waves of panic radiating outwards from the site, and to pacify the TV film crew who turned up too late and were almost disappointed not to find a glowing crater!

Terry finished the evening with the almost obligatory book signing and seemed in danger of being mobbed as the crowd surged forward. It seems hard to believe that there are still people who haven’t heard of the Discworld, and yet as I was talking to my brother on the phone about the event he asked -