It's a long while since one of Irvine Welsh's scurrilous works has made it to the screen (the last one was The Acid House in 1998, only two years after Trainspotting), but that's about to change. Rob Heydon's version of Ecstacy is in post-production, and Welsh has just revealed that Filth is next, boasting a rock solid cast that includes James McAvoy, Jamie Bell and Alan Cumming.

Like an Edinburgh version of Bad Lieutenant, Filth (first published in 1998) is about the monstrous copper Bruce Robertson, nominally investigating a race-related murder, angling for promotion and lots of overtime, steaming through a drug-fuelled week in Amsterdam, making sexually harrassing phonecalls to his friend's wife in the voice of Frank Sidebottom, and afflicted by a tapeworm that acts as his conscience. He's like Begbie, if Begbie was in the "polis". And like Begbie, the weird thing is that you sort of like him in spite of everything.

McAvoy will be Robertson, and this is presumably the role he described as "extreme" and "full-on mental" earlier this year. Bell will be his young partner Lennox, who in the book has some entertaining discussions with Robertson about music, and got his own follow-up in Welsh's 2008 novel Crime. And Cumming gets to be Robertson's beleaguered boss, Bob Toal.

Welsh is acting as producer, and the director is Jon S Baird, whose film Cass Welsh much admired. "Jon and I hit it off and became good friends," Welsh tells The Playlist. "I’ve been trying to Filth made with different producers and directors for years. Jon did a revised screenplay which was absolutely brilliant: he’s captured and kept the essence of the main protagonist but he’s done a lot of interesting things with it as well. He’s kind of rendered it very, very cinematic and it’s going to make a great film with that cast.”

Shooting on Filth starts in January next year. Ecstacy is out in October and we're promised a trailer shortly. Now, what about that Trainspotting sequel?