Within the first ten minutes of Trainspotting, I’d been hauled into a neon-pumping rave, witnessed full-frontal nudity and been called every expletive under the sun. Behind me a couple had left in apparent disgust and around me people were glancing down or laughing nervously into their drinks. Audiences are never entirely sure how to behave in immersive theatre, even at its most gentle; but In Your Face Theatre’s Trainspotting drags you remorselessly away from the haven of the immune and the traditionally invisible audience, pulling you up and pushing you into the sickly, sweaty spiral of Edinburgh’s drug-scene.

The story itself needs no introduction: over two decades since the novel was first published by Irvine Welsh and, not long after, immortalised by Danny Boyle’s acclaimed film, Trainspotting has become a cult-classic, approved by the art-house and the academy crowds alike. However, this “old dog” that Welsh himself has resigned to the critics, has been revised and refreshed by In Your Face Theatre. Injecting speed, the plot has been edited with themes and side storylines cut to create a pure and high-octane 65-minute fix.

Following Renton, Sick Boy, Begbie, Spud and Tommy through the dark streets and rooms of a decaying Edinburgh, Trainspotting follows the lives of the addicts, revealing the extent to which speed and heroin control their relationships, actions and futures. This is particularly evident through the character of Begbie, played by Chris Dennis. Dennis’s relentless energy in conveying the instability and unpredictability of Begbie’s violence is utterly terrifying. But it’s the comic scenes which prove to be the most harrowing: after buying rectal suppositories in order to ease the process of quitting heroin, Renton (played by Gavin Ross) is struck by withdrawal symptoms, suffering a chronic and immediate bout of diarrhoea. Quite literally exploding on the nearest toilet, Renton remembers the suppositories he has just released, and searches frantically through the contents of the bowl. The flecks of bodily fluids that spatter around the space and drip slowly down from the edge of the bowl quite literally leave a bitter taste in your mouth. Trainspotting is harsh and direct and downright disgusting.

At times the plot gets confusing, and as lost as the characters whose lives it traces. Development is not always clear, yet perhaps it is not meant to be: the trippy, suffocating performance space traps all the characters, raising tensions and causing inevitable tragedy. After one tragic and sobering scene, Renton turns desperately to inject himself. In this moment such is the raw emotion and force, it made me wonder – in morbid curiosity – if Ross was actually going to stick the needle directly into his vein. He didn’t, but the perceived boundaries of the unreality of theatre had already been broken.

I rarely come away from the theatre with the feeling that I’ve seen something relevant and real, but In Your Face Theatre’s Trainspotting achieves this, in a way that demands attention through shock, but also through impressive skill.

Trainspotting is currently playing at the King’s Head Theatre until 11 April. For more information, see the King’s Head Theatre website.