IS OUR sexuality pre-determined? Is it linear? Are we all, to a degree, bisexual? What about the notion, as argued by David Bowie, that it’s not the sex of the person which captures our intrigue, but their personality – and how they make us feel?

These questions, and many more, are thrown into the wash that is Mike Bartlett’s play, Cock, set to run at Glasgow’s Tron Theatre. And what become clear is the colours in the mix all run delightfully.

The story tells of young man, John, who, after his long-term relationship with a man breaks down, meets a woman and falls in love. But he is wracked with guilt and indecision about who he is and what he wants. Now John has to make a choice.

James Anthony Pearson, who stars as John, suggests that linear sexuality is more a sub-theme of the play. “The play does explore that notion but John doesn’t really want to think in those terms. He prefers to think he is what he is and he likes these two people for different reasons.”

It’s an interesting idea; you can fall for people not based on their sexuality but because of the role you take up within the relationship?

“Yes, exactly,” says the former Scottish Youth Theatre actor. “The woman allows him to be a romantic, a dreamer, and she doesn’t interrupt him. She allows him expression, and he’s sexually attracted to her as well. But he’s in the relationship with the man because the man is stronger. John likes not having to be strong, and not having to think; everything happens for him.”

Tron Theatre Company’s production of Mike Bartlett’s sharp and witty play will be the first UK staging since its Royal Court premiere six years ago.The actor, who was born in Lancashire but brought up in Aberdeen, maintains it’s a play he simply had to do. “I think it’s one of the best plays I’ve ever read. I wanted to appear in it since I read it four or five years ago and when I heard Andy Arnold (the director) at the Tron was doing it I emailed and said ‘Please let me do it!’

“I love the writing. The characters (the other two are simply called Man and Woman) don’t know how to articulate what they want to say. They ramble and a lot of it is stream of consciousness. But I think that’s brilliant. The lines sound like music.”

The play also explores the idea of whether or not relationships are finite; if there is a sell-by date on dating and commitment.

“It’s about the notion of romantic love versus the reality that is a long term relationship. And it questions why people remain in long term relationships. John, for example, is very weak. He can’t make decisions. Others make them for him. But what we do learn is that all three characters should leave the triangle. Yet, somehow they can’t.”

Some audience members will argue people are essentially gay or not. Yet this play suggests otherwise?

“Mmm. I’m in a long-term relationship, with a man, and that’s very much who I am. But I think there is a spectrum. And I know people who are in heterosexual relationships who have skeletons in their closest.”

He adds, with a wry smile: “I think that’s where the problems emerge. It’s the secrets. But this is where Mike Bartlett has been very clever. His character John is likeable because he’s open about everything. He has sex with his male partner and talks about being in love with the woman, and when he’s having sex with the woman he’s talking about his boyfriend.”

James Anthony Pearson is perfectly placed to play such an angular character, a man who is conflicted yet selfish, assured of his sexuality yet pragmatic, and weak enough to explore.

Pearson, now 35, has revealed his considerable range in TV drama such as Lip Service and film Control, in which he played New Order frontman Bernard Sumner. “The success of that film came as a real surprise to me,” he recalls. “It had an unknown actor as a lead, unknown director, and was filmed in black and white. Who would have guessed?"

The actor picked up powerful reviews for his performance. “Thanks,” he says, in grateful voice, “but I felt like I was a Barbie doll when it came to meeting the real people.”

He always wanted to act (“It’s part of who I am as a person”), but in spite of his SYT and school drama experience, didn’t take off to drama college, but instead studied maths and physics at Edinburgh University. “Going to drama school just wasn’t done in my family. So my plan was to go to uni to study something I was good at, and then take up acting on the side. I joined the Footlights and while at uni I auditioned for a part in a TV series called Jeopardy (the children’s sci-fi series set in Scotland and Australia). And I got it, from a hundred or so others, and it was brilliant.”

University was jettisoned. “I tried to continue the degree while in Australia, via the Open University, but there I was on set working out complex analysis equations and thinking ‘Why the hell am I doing this?’”

He was right to question his common sense; the acting work kept on coming. But that’s not Pearson’s only talent. He has secured funding from Creative Scotland to write his own screenplay, featuring the young Stan Laurel. “I wrote a spec screenplay a couple of years ago and thankfully I’m now working with a script editor in London,” he says, with clear delight in his voice. “I write for two hours each morning before coming to rehearsals and I love it.”

Was he a Stan Laurel fan? “I knew of them. I learned more about Stan when I did a radio play about his life when he appeared at Glasgow’s Panopticon Theatre. But my film isn’t about Laurel and Hardy, it’s about how Stan finds his character. In researching the radio play I discovered he was part of a double act with a woman called May. It was a dysfunctional relationship. He would be beaten up by this woman who was brilliant on stage, but not so great off stage.

“He stayed with her ten years on stage. But it made me wonder why. Was he the battered wife in this case? Did part of him wish to be controlled? Did he feel dependent on the talent she brought to the act?”

Are there Cock-like themes in here? “That’s definitely the case. Again it’s a functioning dysfunctional relationship in which both parties stay together and choose to be miserable because they are scared to be alone.” He adds, grinning: “And it all makes for fascinating drama.”

•Cock also stars Johnny McKnight, Isobel McArthur and Vincent Friel and is at the Tron Theatre Glasgow from tonight to February 20, The Lemon Tree Aberdeen on February 23, and the Traverse Theatre Edinburgh, February 25-27.