FLASHBACK: Twenty-odd years ago, a little boy stands excitedly in a cinema queue in Glasgow’s south side. He’s wearing the tragic fashion ensemble that is double denim because his tiny head has determined this urban cowboy effect is likely to make him look older, and thus help gain entry to a 12 Certificate film.

To his amazement – and delight – he’s allowed entry. And for three hours and 15 glorious minutes he stares up in wonder at Leonardo DiCaprio and in particular, the talent that is Kate Winslet. in Titanic.

Fast forward to just over a year ago. That same little boy, James McArdle is now an actor and finds himself working on location in a film, Ammonite.

It’s McArdle’s birthday and as he steps into the make-up caravan, he spies a package with his name on it. “I opened it and pulled away at layer after layer of tissue paper – and eventually I uncovered what was a little blue music box with pictures of the ocean on it,” he says in such excited voice you can almost imagine it emerging from the throat of the little boy from Darnley. “It was covered with pics of Kate and Leo DiCaprio. And when I opened it played My Heart Will Go On.”

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The actor breaks into a Titanic-sized smile. “That was my birthday present from Kate Winslet. I had told her about queuing up to see her in Glasgow and she thought it so sweet. And she knew I was getting a flat at the time, and said I could put the music box on my mantelpiece.”

The story is poignant for several reasons. It underlines the sheer unpredictability of life. It highlights how solid friendships can blossom from the most unlikely beginnings. “Kate is incredibly professional and generous and such a brilliant actor,” he enthuses.

“What also strikes me [about her] is her staying power, which is so unusual in Hollywood these days. She really has become a Meryl Streep. She has this transformational ability.” He adds, “Saoirse [Ronan] is also terrific.”

Ammonite is a much talked-about 19th century story, a wrenching tale of sapphic sexuality set against a Dorset backdrop of fossil discovery. Winslet plays the real-life bone hunter scientist Mary Anning and Saoirse Ronan is Charlotte Murchison, the married aristocrat with whom she develops a special relationship.

McCardle plays her husband, Roderick. “I loved making the film,” he says.” I loved what the director Francis Lee did with it. He gives you space to think, to decide what you think of it.”

The Glaswegian was delighted he had the chance to play a toff. “Even though I’ve been to RADA and I have a classical training it’s still rare I’d get seen for the role of an aristocrat. I was so grateful Francis took the chance on me. But I also think that when someone is cast as the opposite to their own character, it can help shed new light and take you away from the stereotype.”

HeraldScotland: Kate Winslet in AmmoniteKate Winslet in Ammonite

He adds, with a wry grin: “There may be a warmth you get from a working class Scottish person that you wouldn’t get from an upper class English person.”

When filming was over, Winslet didn’t forget her young Scots chum. “She’s special,” he says. “I did Peer Gynt at the National and she came to see it.”

But Ammonite didn’t signal the end of their professional relationship. Last year, McArdle landed a key role in a new HBO crime murder series Mare of Easttown, set in Pensylvania, again alongside Winslet.

Was he not tempted to say ‘Come on, Kate, are you following me around?’

“Yes,” he laughs, “and if I had she would thought that funny.”

What is there about the young man from Glasgow that not only Winslet, but a range of directors, from the National Theatre to the Royal Court, to TV series such as Love And Marriage (in which he starred alongside Alison Steadman and Ashley Jensen) that makes him a stand-out? What’s taken McArdle to an Olivier nomination and an Ian Charleson Award?

Well, he certainly has drive. Once a shy child, he was sent to Paisley children's theatre group PACE to instil a little confidence. Aged 14, drama teacher Mhari Gilbert took a group down to Stratford to see Matthew Macfadyen play Romeo. McArdle fell in love with acting. “I knew then I would go to RADA,” he said later.

HeraldScotland: James McArdle in AmmoniteJames McArdle in Ammonite

Aged 17, the teenager pulled the money together to take the bus to London for his RADA interview. But the interview was a disaster. He fluffed his lines, yet was bold enough to go back and ask for a second chance. It paid off. He was in. And then he was out before he graduated, having already landed the role of Malcolm in Macbeth at the Globe Theatre. Since then McArdle also played the role of James 1 in Rona Munro’s James Plays.

Yet, the young Scot has his achievements in perspective. “To be honest, I don’t really think about the success. What I do know is that there’s no real rational to it. Some of the best actors I know never seem to get work. And some of those I don’t think are that great work all the time. But it’s not someone’s fault if they get the work someone else should have.”

He sighs; “It’s the life we sign up for. All you can do is not be precious and work hard, and remember that no one owes you anything. That’s why I really appreciate the support I’ve had from Jonathan Kent at the National.”

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He reflects: “It’s not a modern thing to invest in an actor’s career any more. Directors have their own lives to think about. But he’s always pushing me. When he brought Peer Gynt to me I wasn’t sure I could manage it, it seemed so undoable. But he kept saying ‘This will make you better.’”

The Scot talks of how the business of acting is certainly more challenging for those who don’t come from a privileged background, of the need to pay the rent. Yet, he adds that it’s a calling. "I think you are born an actor but where I was lucky was my drama teacher at PACE encouraged me to be cheeky, to have the drive, or arrogance if you want to call it that. I think casting directors pick up on that.”

McArdle has lived in London. He’s appeared on Broadway. And he’s been filming in Pennsylvania. Now he’s moved back to Scotland permanently. When Covid struck, he left America and moved back in with his parents in Darnley.

He grins when he speaks of how it has all been a little surreal. “One day I was up in my childhood bedroom, having a Zoom call with a big Hollywood director, and all I could hear from downstairs was my dad yelling out; ‘James! That’s your dinner ready!’”

He is no longer living with his parents. “I’ve bought a place in Glasgow because this is where I want to be. I never really felt that I could grow roots in London. It used to be the case that you had to be in London to work as an actor, that’s no longer true.”

His commitment to Scotland emerges in now becoming a patron of PACE, which is in the process of creating Exchange Paisley, a new 200-seater community theatre space set in a former telephone exchange.

Would McArdle like to work more in Scottish theatre, with NTS for example? “I’ve met some Scottish theatre directors and I really want to do plays here.”

Perhaps Oran Mor, Glasgow’s basement theatre in the West End? “I would love to do an Oran Mor,” he says in excited voice.

McArdle is certainly excited about his future. But a searching question about his past has to be revisited. Does he think he gained underage access to Titanic as a result of the double denim after all? “Maybe not just the double denim,” he says grinning. “I also wore a watch that day, to help me look older. Although when I think back it was a child’s watch that was green and orange and blue. So, yes, it must have been the denim.

“But either way, it gave me a great story to tell Kate.”

Ammonite (15) is now available on digital platforms