They say actors have to suffer for their craft, whether it be chopping of their prized head of hair or starving themselves to lose weight.

But what about sticking a needle in your arm?

Gavin Ross who has taken on the iconic, toilet-swimming role of Renton in the stage version of Trainspottting says he almost fainted when he had to learn about taking drugs for the role.

“There was a guy who came in and taught us how to cook up heroin properly and I literally stuck a needle in my arm for the poster image. It was pretty grisly and I was pretty pale by the end of it.

“We have had 27 people faint during the performance as well.

“If you don’t like needles, don’t come and see it – especially as we are a company called In your Face Theatre – we do what we say on the tin.“

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The actor grew up in mining community Newtongrange just outside Edinburgh but now lives in Leith, where Irvine Welsh set his gritty 1996 book about a group of addicts in the late-’80s, which was adapted for the stage shortly afterwards by Harry Gibson.

Gavin says: “It was pretty haggard back then, people began to share needles and Edinburgh became the HIV capital of the world.

“You speak to people from that time and they say they are the last from that time from their block of flats. It’s pretty intense and the scars are still visible.

“It’s a lot safer now and their rehabilitation programmes, the crime rate has dropped because there’s lots of CCTV, but it’s still an issue that is prominent so I think our production does have a message for this day and age.“

The 22-year-old was 15 when he read the book and 16 when he saw the graphic 1996 film adaptation starring Ewan McGregor.

“To me he was Obi-Wan Kenobi, so it was a bit bizarre seeing him go down a toilet.

“I just remember how explosive and powerful Robert Carlyle was as well, that had a big impact on me.

“I was the kid in school who would constantly quote the film, to the chagrin of my classmates.“

He was offered the role without even auditioning after bosses saw him a production of The Hard Man and says it was a “dream come true“.

He has performed the play more than 100 times. At one performance Ewan Bremner, who starred as Spud in the film, was in the audience and another time Irvine Welsh watched him.

“Meeting him was mind-blowing,“ says Gavin. “He was very complimentary.“ Now he is excited about bringing a fresh version of the production down to London with an all-Scottish cast.

“The first time I performed it, it was a three-hour long show with no interval and was a lot more intense.

“For this London run I have stepped back from the intensity and am focussing more on the story he’s telling. More so London ears can understand it, but we are still retaining that Leith authenticity, we can’t sell out.

“Finding that balance has been interesting.“

King’s Head Theatre, Upper Street, Islington, until April 11. Details: 0207 226 8561, kingsheadtheatre.com