HARRY Gibson was working as a script-reader for the Citizens Theatre when he stumbled across Trainspotting, Irvine Welsh's iconic novel of 1980s Leith life that went on to become a phenomenon. It was the early 1990s, and the equally iconic Citz had just opened its Circle and Stalls studio spaces in the image of the long gone Close Theatre, with the intention of producing cutting edge new and experimental work with little financial risk.

Not to make too fine a point of it, a lot of the stuff landing on Gibson's desk wasn't that great. In search of the holy grail, he went off to John Smith's bookshop, a legendary and now lost emporium on Byres Road, where he asked if there was any new Scottish prose fiction he should be taking a look at. Eventually, Gibson was handed the last battered copy of Trainspotting they had in stock. The book, which charted the hedonistic adventures of a group of young Leithers in 1980s dole queue Britain, was already being devoured by a young readership in search of something to excite them, and copies of it were scarce. Gibson got on a train and began reading.

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“I got as far as page thirty-eight,” Gibson remembers on the eve of the Citizens' main stage revival of his adaptation by director Gareth Nicholls, “and I rang Giles and told him to buy the rights to the book immediately before anyone else did. I knew straight away that here was a work of genius crying out to be done onstage.”

Then Traverse Theatre director Ian Brown's production of Gibson's adaptation, written for four actors, was originally seen at the Traverse and then the Citz's tiny Stalls Studio. Welsh's anti-hero Mark Renton was played by Ewan Bremner, who would go on to play Spud in Danny Boyle's big-screen version of the book. Susan Vidler, who played all the female parts onstage, would also appear in the film, which would transform a cult book that became a stage sensation into a mould-breaking global enterprise (both Bremner and Vidler had appeared in Mike Leigh's film, Naked). Malcolm Shields and James Cunningham completed the onstage quartet.

Arriving in a landscape where youth culture was about to burst wide open, Trainspotting in all its forms had already got the party started. Gibson's play was lumped in with an energetic new wave of dramatic writing that became known as in-yer-face theatre.

“I'm responsible for dirty theatre,” Gibson chuckles, relishing the association. “What became known as in-yer-face theatre was hugely influential on telly shows like Skins and Shameless. Of course, there were pre-cursors, like Steven Berkoff and so on, but I'm perfectly happy to be part of a new tradition. The thing with Irvine is that he's totally non-judgemental, and he loves the dirty side of life anyway. One always worries about doing things about other people's pain, but in Trainspotting, in the midst of all this s***, people are living a life, and in the end it's righteous.”

Read more: Pictures: Filming gets underway for Trainspotting sequel

Following it's original run at the Citz, Trainspotting was picked up by commercial producers, G&J Productions, who toured it with various casts for the next decade.

“Once the film of Trainspotting came out, it kind of went ahead of us as a trailer,” says Gibson, “the only downside of which is that people sometimes expected our play to be a stage version of the movie, which was like the Monkees or A Hard Day's Spliff or something. What we were doing was much darker.”

Following the success of Trainspotting, Gibson went on to adapt Welsh's third book, The Marabou Stork Nightmares, which was also picked up by G&J following its initial run at the Citz. This was followed by a solo version of Welsh's novel, Filth, initially performed by actor Tam Dean Burn in the Stalls Studio before moving to the main stage. The last of Gibson's Welsh adaptations to be seen at the Citz was Glue. A stage version of Welsh's sequel to Trainspotting, Porno, was written, but has yet to be produced.

Gibson's relationship with Welsh continued with Blackpool, a musical penned by the novelist with post punk icon Vic Godard, whose band Subway Sect played with the Clash at Edinburgh Playhouse in 1977, switching Welsh's generation onto myriad possibilities in the process. While Blackpool has never been seen professionally, Gibson directed a production featuring drama students at Edinburgh's Queen Margaret University, then situated on Leith Walk, the heart of Welsh country.

“I never found much interest in Edinburgh for doing Irvine's work,” says Gibson. “Blackpool was a glorious failure, but it was interesting working with a young cast who were willing to try anything. After that everything sort of dried up. If anyone had been on the phone asking me to do another adaptation of Irvine's work I'd have done one, but once the old guard of the Citizens left they didn't want it. It's rather lovely that the new people want to do Trainspotting again.”

Read more: Pictures: Filming gets underway for Trainspotting sequel

For Nicholls, the importance of Trainspotting for a younger generation of theatre makers was a no-brainer.

“For me it was the politics of the piece,” he says. “At the story's heart are these disenfranchised characters who are trying to escape, but who are all trapped in this 1980s Thatcherite landscape. It feels that in the times of austerity and disenfranchisement that we're living in now that we've come full circle, and the play so speaks to now. There's a beautiful symmetry as well in terms of the play having started at the Citz, it being the twentieth anniversary of the film, and also with Trainspotting 2 being filmed just now as well.”

In terms of the politics of Trainspotting, Nicholls may be onto something. While at the time many in-yer-face plays seemed to lash out with a fury that seemed to define an age of disenfranchisement with little to believe in, they now seem to represent a moment of taking stock before regrouping and refocusing on the political struggle ahead. Gibson for one isn't surprised that Trainspotting in all its guises has become a totem of popular culture in a way that has transcended its 1990s origins to become a defining signifier of the counter-culture.

“The thing is,” he says, “in theatre, because we live our lives on the razz a bit more than a lot of people, we're a bit more culturally ahead of things. At one time, the church was on one side of the street, and the playhouse was on the other, and we're well aware of this idea of sympathy for the devil. That goes right back to hippy times, and then punks, goths, emos, and whatever we call it now, where it's like a kaleidoscope, and where you can go to a music festival and see seven different types of music and not worry about tribes. Trainspotting was a punk book and a punk play,” says Gibson. “We're all punks now.”

Trainspotting, Citizens Theatre, Glasgow, tomorrow(September 14) to October 8.

www.citz.co.uk