The lead role in Kes is so intense it’s taken someone twice his age to play Billy Casper. Katherine MacAlister investigates.

It’s OK actually, because I always get ID’d when I buy booze and cigarettes anyway,” Stefan Butler tells me grinning, when I ask how hard it is for a 28-year-old to play a 15 year-old boy.

“I also have a small build and am blessed with a babyface,” he laughs.

“And I’m good at mentally regressing,” he adds.

What he doesn’t say is that he plays Billy Casper brilliantly, the lead in the haunting play Kes, leaving no one in any doubt that, on stage at least, he is a teenager through and through.

“The hardest thing is actually making sure I get time to be a 28-year-old when I’m not on stage, because people do get quite patronising.

“They forget that in real life I am a grown-up.”

That says it all. The transformation is so complete that even his fellow cast members think he’s a real-life Billy Casper.

For those of you who haven’t come across Kes, it’s Britain’s version of The Kite Runner, adapted from the book A Kestrel for a Knave.

Brought out in the late 60s, it’s about Billy escaping from his neglectful mother, dysfunctional family, and bullying school.

He finds salvation in a stray kestrel and learns how to cope and stand on his own two feet through the bird-of-prey.

For Stefan though this pivotal role means two hours of non-stop acting.

“I’m a slow, calm person and reserve my energy for roles like this,” he tells me.

So where did he learn to be such a convincing teenager?

“My girlfriend is a teacher and I work in her school and in youth theatres around the country so I’m surrounded by teenagers a lot of the time.”

Why they chose someone of Stefan’s age is another question.

“They auditioned hundreds of teenagers for the part between the ages of 16 and 18, but it’s a 10-week tour and you spend the whole time on stage. Plus there are so many emotions that Billy has to go through, I think it was too taxing.

“But for me, this is the sort of role I hoped for when I studied drama and I’m loving it, although one day it would be good to play someone my own age.”

So how does Stefan cope then? “A lot of bananas,” he grins. “To start with after the play I would go to the bar with the cast and they would by me a pint and I would only manage a few sips by last orders. I just sat there staring into space as if I was shell-shocked.

“It’s definitely the most intense role I’ve ever played because everyone puts Billy down and I care about him. But I’m coming along now, by the time I get to Oxford I’ll be able to do it in my sleep,” he jokes. “I might even manage a few pints by then.”

Kes opens at the Oxford Playhouse on Monday. Call the box office on 01865 305305.