The 86-year-old actor, best known for his acclaimed stage work and iconic roles such as Gandalf in The Lord of the Rings and Magneto in the X-Men films, has described his latest part as the role of a lifetime.

The Bolton School old boy has long been regarded as one Lancashire’s most celebrated actors, even though his career has taken him around the world. Over the years, he has often spoken with pride about his Bolton roots.

He has also returned to the area on several occasions, including visits to Albert Halls to celebrate his 80th birthday.

His latest film, The Christophers, directed by Steven Soderbergh, sees him play Julian Sklar, a once-famous but washed-up painter whose estranged children hire a forger to complete several unfinished canvases abandoned years earlier, hoping to secure an inheritance when he dies.

Set in London, the film also stars I May Destroy You creator Michaela Coel as Lori, an art restorer and former forger, alongside Baby Reindeer star Jessica Gunning and Gavin & Stacey co-creator James Corden, who play the siblings.

“I was relieved when I first read the script, as it was such a wonderful part of a lifetime,” he says.

“Julian was a wonderful talker. He talked a great deal for an artist, as artists don’t always talk much, and I was relieved.

“Although the film is very much about art and where art comes from, it’s about a lot more than that. It’s about family, love, regret, old age and London. Lots of other things. It’s nicely complicated and a rattling good yarn as well.”

The film feels at times like a two-hander play between Sir Ian and Coel, both of whom have theatre backgrounds.

(Left to right) Iain Canning, James Corden, Sir Ian McKellen, Michaela Coel, Jessica Gunning and Jim Parks arriving for The Christophers London premiere at the Picturehouse Central in London (Image: IAN WEST)

Sir Ian praises his co-star and her remarkable talent.

“I learned an enormous amount from Michaela. With some surprise and regret, I realised that all her life she’s lived within a mile of where I’ve lived in London, and we’ve never met.

“I never saw her in the street; she went to school just 500 yards from here.”

He adds: “She’s a little bit unnerving, as not only is she a startling physical beauty, but she’s also extremely intelligent.

“She’s great fun, which is a relief, but there’s talent in every direction, not just as a producer, but as a playwright, director, and actor.

“She was very, very nice to me and kind, and we got on straight away, which we needn’t have done, because the characters are rather abrasive at least at first. How could you not like coming into work?”

In the film, Julian was once a star of London’s 1960s and 70s pop art explosion, but he hasn’t painted in decades and has been broke for years.

He lives in a crumbling but expansive London townhouse and makes Cameo videos for fans to earn money.

Commenting on his own long-lasting career, Sir Ian says: “Well, there’s a distinction between what I do and what Julian does. He’s an artist. Everything comes from inside him, and it’s his stroke on the brush on the canvas that makes his art.

He very modestly adds: “My art is second-hand. Somebody writes my words, and they tell me sometimes where to stand to deliver them, and give me directions as to how I should speak them. I’m there to interpret other people’s art and deliver it.

“You can go on as an actor until the day you die, as long as you get insurance and your voice and knees show up. If I were a writer, I would have to come up with new material to write, but other people do the writing.”

In the film, it is revealed that the reason Julian hasn’t finished The Christophers paintings is due to a broken heart.

“Once it occurred to us both that the reason the old boy hadn’t completed the series of Christophers, and that they remain in his attic unfinished, was a broken love affair,” he explains.

“It really turned him off painting altogether and destroyed him, that was a wonderful thing to know about the character. That love could be such an important part of his makeup, even though he now loves nobody but himself.

“Perhaps there was a time, and I don’t mean to make one too melancholy, but it did me in a little bit,” he adds emotionally.

We end the interview discussing the enduring power of great art and the need to support the arts.

“I’ll tell you one simple thing that rather puzzles me. I remember working with John Schlesinger (the British director who won an Oscar for the 1969 film Midnight Cowboy), and in his latter years he didn’t make films,” he says.

“He set up films. He had ideas for films. He wrote films. He encouraged other people to write them. He raised the funds, or didn’t.

“That man should have just been given a pension by the government to make whatever films he wanted, and if we’d done that, there would have been six more John Schlesinger films that never got made.

“If it happened, I think, you know, you hear of ‘national treasures’, I wouldn’t mind if you introduced that title, and with it would go a pension so that someone didn’t have to think about money.”

He adds: “Of course, great artists in the past have always had patronage, Michelangelo, Da Vinci, everybody. But we’ve forgotten how to subsidise the arts in a way.

“Even in my youth, we used to go to the theatre, and I would think that would be the easiest way to encourage that art to go on being made.”

The Christophers is in UK and Irish cinemas on Friday, May 15.