James Mottram

Jack Reynor has a request before we get started. "A cup of tea and some Paracetamol," he asks of the obliging publicist. It's just after 10.30am and last night, the 23 year-old Irish actor was with a friend in London who'd worked on A Royal Night Out, one of two new films Reynor has coming out. To be fair to the lad, he doesn't look so bad after a night out on the lash; doodling with a pencil on a pad in front of me, the bearded, blue-eyed boy from County Wicklow is what you might call a handsome devil.

Already, Reynor has made an impact. His fine performance as an alpha-male teenager in What Richard Did caused enough ripples to reach Hollywood. Before he could blink, he was cast in last year's Transformers: Age Of Extinction alongside Mark Wahlberg and those giant metallic robots. But now he's back on home soil with Glassland, a stunningly acted drama in which he plays a cabbie lad from Dublin who is desperate to help his alcoholic mother (played by Australian actress Toni Collette).

It was the experience of making Transformers, he said, that led to Glassland. "I'd spent a year in the States. I hadn't come home once and I was really missing Ireland. And a lot of things had changed for me in a very short space of time. So when I finished Transformers, coming home to Ireland, I really wanted to get back in touch with the place and ground myself there, and re-discover what I wanted and define which direction I wanted to take in my career."

To his credit, Reynor's planned path was not simply to hop onto the next "big franchise", make "loads of money" and engineer a "big profile", he says. Preferring to aim for performance-driven work, Glassland fit perfectly. "I was able to commit myself to it in a way that I probably wouldn't have been had I not gone away and done Transformers," he notes. And commit he does; his work with Collette - who goes so far from her sunny Muriel's Wedding persona - is utterly heartbreaking.

Reynor, who was born in the US, was raised by his mother, Tara, a human rights defender, in Ireland. Without going into specifics, he adds, "I have a lot of family who would be similar enough to the family in this film." But he felt he didn't want to research alcoholism too closely. "For me, it wasn't so important to immerse myself in the culture of alcoholism. I think that you can be addicted to f***ing smarties and have the same processes."

Alcohol, he clarifies, is not the issue. "It's the aggression and the confusion and the tension inside a person's head. For the people who are around it, it's not knowing what you're going to see when you walk through the door and who's going to be on the other side of it. That was what was scary about filming the movie. It was going into that place...I think we were all very vulnerable in a sense. But we went for it anyway and we're happy with how it turned out."

Impressively, Reynor has stuck with Irish film since completing Glassland. He's shot Sing Street, the new teen-themed movie from Once's John Carney, and The Secret Scripture, directed by veteran Irishman Jim Sheridan and co-starring Rooney Mara. "People ought to take Irish films a little bit more seriously than we all drink pints of Guinness and strum guitars," he says. "That's not the kind of society we are; we're a lot more complex than that."

He then makes reference to The Guard and Calvary's director John Michael McDonagh, who "had a few things to say about the state of Irish film" in an interview that was conducted with the Associated Press. "He felt it [the Irish film industry] was inadequate and our crews were terrible. All these kinds of things. I think that is a really unfair thing to say. I think we're in a better spot than we've ever been... there, and lots of really good young Irish actors and writers and directors and producers."

Reynor points to Michael Fassbender, "absolutely killing it" out in Hollywood; they met through a mutual friend, Lenny Abrahamson, who directed Reynor in What Richard Did. "We had a few nights out together which was good fun, and he [Fassbender] gave me some pointers before I went away to do Transformers, which was much appreciated." He's since got to act with Fassbender in a hugely anticipated movie version of Macbeth, due later this year.

Playing the monarch Malcolm (with Fassbender and Marion Cotillard as Macbeth and Lady Macbeth, respectively), Reynor went to the set of the Scottish play directly after shooting Glassland. Intimidating? He nods. "They hadn't heard my Scottish accent. I'd never performed in Shakespeare. It was my first period film. And that was all scary stuff but at the same time, I find when I'm in an intimidating position, that's often when I can draw the best out of myself."

Before Macbeth, however, Reynor has fantasy-romance A Royal Night Out. Reynor plays a disgruntled soldier who meets the future Queen of England, Princess Elizabeth (played by Sarah Gadon), as she covertly joins in the celebrations on V.E. night. To emulate this, Trafalgar Square was roped off and dressed like it was 1945. "It was crazy to experience that for a moment," he says. "It was like looking through a window back in time." Whether he needed any Paracetamol after that particular night out, he doesn't say.

Glassland opens on April 17th. A Royal Night Out is released on May 15th.