Irvine Welsh is writing a follow-up to his novel Trainspotting, the book that spawned the film that started a run on Edinburgh-English dictionaries after the world was left wondering what exactly a blue-nosed Weegie gadgie was (that's an underprivileged member of the Glasgow Protestant community to those south of the border.)
Welsh, who has always poured cold water on talk of a sequel, read two extracts from the manuscript to rapturous applause at the Edinburgh books festival.
Fresh from running a half-marathon, he said he had been "a bit of a lazy bastard", so its publication had been put back a year. "The truth is it's taking so long because I'm really enjoying writing it. I knew there was more life in the characters. I had written a huge amount more of Trainspotting than went in the book, but I didn't want to rehash that."
Trainspotting, Welsh's first novel, became an instant sensation when it was published in 1993, even though it was written in working-class Edinburgh dialect so dense that well-heeled New Towners had difficulty understanding it. It went to 14 reprints even before the film sent it to the top of bestseller lists around the world.
The four surviving characters from the series of interweaving short stories - Mark Renton, Spud Murphy, Sick Boy and the Begbie - will feature again in the new book, provisionally titled Porno.
Welsh has stuck to the same format, but if anything the writing is sharper and even funnier.
Sick Boy, the Boswell of barbiturates and the world's leading authority on Sean Connery, has finally realised his dream of directing films; unfortunately they are of a pornographic nature. Spud, the most spaced of the four, is still struggling with his heroin addiction and has bizarrely taken to writing a history of Leith, from whose sink housing schemes all the main characters sprang.
Welsh was more reticent about revealing details on Mark "Rent-boy" Renton and alcoholic psychotic Begbie, the characters which helped to launch Scottish actors Ewan McGregor and Robert Carlyle to Hollywood stardom. "I can't say what is happening to Renton and Begbie - that would be too much information, but they do get back together," he said.
He also revealed that he was toying with the idea of introducing a new character, in the form of a journalist-turned porn starlet.
Picking up their stories 10 years after Trainspotting finished, the new book will be set in the same milieu of low-life Leith "scumbags and bampams", although large parts of the area notorious for squats and crack dens have now been yuppiefied. Smart restaurants and bars may have sprung up all around, but Welsh claims that life in the schemes is still as grim as it was. Nor has Leith's small army of streetwalking prostitutes or its Aids problem gone away either.
"There's bits from London, Amsterdam, San Francisco and the south of France as well, but it's mainly Leith, which is more interesting anyway," he said.
Danny Boyle's film of the original book, in which Welsh had a cameo role as a drug dealer, was one of the outstanding British films of the last 20 years, however Welsh insists that he does not have one eye on a screen sequel. "I'm just concentrating on the book, I've a lot of it still to go. It does nae help to start thinking about a film; they are very different things anyway. You don't write a book so someone can make it into a film."
That Welsh chose the Edinburgh books festival to reveal that he was writing the sequel has a certain symmetry. Trainspotting's most famous scene takes place on the first day of the jamboree, when Renton dredges through his own excrement in a bookie's toilet, searching for the opium suppositories he has inadvertently evacuated.
It is just this sort of glorying in the squalid, however, that has made Welsh the target of stinging criticism from two of Scotland's leading writers. The award-winning novelist Ronald Frame used a speech at the festival at the weekend to attack the "cliched brand of novels celebrating such dark subjects as cannibalism, necrophilia and sado-masochism" written by the likes of Welsh and the Booker Prize winner James Kelman.
Tomorrow the poet Kenneth White will go further in another address, comparing their grittier-than-thou realism to the "remains of last night's fish supper, sauced up with sordid naturalism".
Welsh, who has a book set in Sudan coming out later this year and is also writing a love story set in Bangkok for the BBC, is having none of it. "I've never thought of myself as a realist. I don't think that talking tapeworms and squirrels is all that realistic. I understand what they are saying, but when somebody sells more books than you, you are always looking for an excuse. It tends to come down to: 'I hate that bastard because he sells more books than me.'
"You can't tell anybody what they should and should nae write. I get people into books who normally don't buy them and this is supposed to be terrible. I don't know what they are moaning about."
Spotted: Where the film's cast are now
Ewan McGregor (Rent-boy)
Now starring in Moulin Rouge with Nicole Kidman, McGregor has been the most successful member of the cast and will soon reprise his role as Obi-Wan Kenobi in the next Star Wars film. He received good reviews for Shallow Grave but Trainspotting propelled him to stardom. Fell out with director Danny Boyle because he wanted Leonardo DiCaprio's role in The Beach.
Ewen Bremner (Spud)
Despite his relatively low profile, Bremner has worked steadily, with sizable roles in everything from Harmony Korine's arthouse flick Julien Donkey-Boy to the hugely expensive but critically panned Pearl Harbor.
Jonny Lee Miller (Sick Boy)
Started promisingly by winning major roles, but the gangster movie Love, Honour and Obey was poorly received and his appearance with Robert Carlyle as a dashing highwayman in Plunkett and Macleane did little better.
Robert Carlyle (Begbie)
His CV rivals McGregor's - but includes The Beach. The phenomenal success of The Full Monty cemented his reputation as a star, but it was his vicious portrayal of Begbie that landed him the part of the villainous Renard in the last Bond movie, The World is Not Enough. He has continued to make lower-key movies too, working with the director Ken Loach on Carla's Song.
Kelly Macdonald (Diane)
The 23-year-old made her debut in Trainspotting and was snapped up for the title role in Stella Does Tricks. Minor roles followed; Robert Altman's star-packed Gosford Park could give her career a boost.
Kevin McKidd (Tommy)
One of the lesser-known cast members, MacKenzie has nonetheless prospered, appearing in Hideous Kinky and Mike Leigh's Topsy-Turvy. Recently his best roles have been on TV in the drama North Square and as Count Vronsky in Anna Karenina.
Danny Boyle, director
The best-known of the team behind Shallow Grave and Trainspotting, Boyle has continued to work with writer John Hodge and producer Andrew Macdonald. They hit the jackpot with their adaptation of Alex Garland's novel The Beach, but it was a bruising experience. Said goodbye to Hollywood, turning down Alien 4. Currently working with Garland on a sci-fi thriller.