BACK in September, Liam Neeson began to admit something to himself. “I thought, I’m just tired,” he says.

Now 64, the Irish actor has been working in the film business for thirty-five years, starting with a role in John Boorman’s Excalibur. Since, he’s notched up films with titans like Steven Spielberg (Schindler’s List), Christopher Nolan (Batman Begins) and Ridley Scott (Kingdom of Heaven). “I’ve been very, very lucky but I tend to go, ‘Oh my God, they’re offering me a film – I better do it!’ How much? I’ll do it!’”

It’s understandable, not least since enjoying a belated late-career run as an action star after the success of 2008 kidnap drama Taken. When we meet in London’s Mandarin Oriental hotel, the 6ft 4in Neeson sporting a navy suit, he’s carrying a thermos flask embossed with the logo for The Commuter – an upcoming train-set thriller by Jaume Collet-Serra, who directed him in Unknown, Non-Stop and Run All Night. “I said to my agent, ‘Do they know what age I am?!’ Maybe another eighteen months and then that’s it…”

Neeson’s work ethic is never more apparent than this week. He’s playing General Douglas MacArthur in the Korean film Operation Chromite, in a story about the Battle of Inchon (“I love reading about history,” he confesses); in A Monster Calls, he’s central to the sob-inducing tale of a boy and his dying mother; and, most intriguingly, he’s a 17th Century Jesuit priest grappling with faith in Martin Scorsese’s long-awaited Silence.

His second film with Scorsese after Gangs of New York sixteen years ago, Neeson – surprisingly – can’t bring himself to call the director ‘Marty’, as he’s known throughout the industry. “I don’t even dare presume to know the man,” he says. Even here, in this adaptation of Shusaku Endo’s book, he’s more presence than person, as Adam Driver and Andrew Garfield’s Portuguese priests arrive in Japan searching for his character, Father Ferreira, after he disappeared on a mission to spread Catholicism.

“My god, you talk about a hostile environment!” says Neeson. “I can kind of understand the Japanese reaction to that kind of colonialism which the Portuguese were after. They always sent the missionaries in first to appease the people and win them over to God. Had no idea of the spirit of duality that was already there because of Buddhism and Zen and all the rest of it. And of course the Japanese were terrified of being colonised and ruthlessly put down the Catholic faith.”

Having been in 1986’s The Mission – where he did a lot of work with Jesuit priest Father Daniel Berrigan – Neeson admits he’s “still questing” in his understanding of the universe. Post Silence, he’s been reading Richard Dawkins’ atheist-themed book The God Delusion, as well as extending his interest in science. “It’s very, very interesting,” he says. “Science will always ultimately answer all the ‘how’ questions but the one they can’t and won’t is the big ‘why’ question.”

In the case of A Monster Calls, the film deals with the horror faced by Conor, a young boy from the north of England (Scottish newcomer Lewis MacDougall) as his mother (Felicity Jones) suffers from a terminal illness. Based on the book by Patrick Ness, the fantasy sees Conor imagine into existence the tree outside of his window. Neeson, via motion capture techniques, plays the resulting tree-monster – a CGI-realized creature that forces the boy to reckon with his own emotional turmoil.

“This poor kid has nobody to turn to – even his mother doesn’t tell him the truth,” says Neeson, softly. “And he’s desperate to be told, the way kids are – kids can handle stuff. To treat them like adults and tell them the big issues in life, if they come up. Like the Easter Bunny – does it exist? Santa Claus? It starts there!” Father to Micheal, 21, and Daniel, 20, Neeson adds: “The story really appealed to me on a very basic human male parent level.”

Born in Ballymena in Northern Ireland, the son of a cook and a caretaker, Neeson has suffered shocking grief in his life too – after the death in 2009 of his actress-wife Natasha Richardson. The mother to his two sons, Neeson met Richardson on a Broadway production of Anna Christie in 1993 and they married a year later. But the daughter to esteemed actress Vanessa Redgrave lost her life following a brain injury she sustained from a skiing accident in Quebec.

Appearing on US show 60 Minutes recently, Neeson gave a rare interview talking about the last days of her life, when she was on life support, admitting they had once made a pact that if either “got into a vegetative state that we’d pull the plug”. It was a frank revelation for an actor who fiercely guards his personal life. Being uncomfortably in the spotlight like this…it’s another reason why he’s found acting more tiring. “Sometimes all the other stuff becomes kind of circus,” he sighs. “There just seems to be no privacy.”

Not the sort of actor you will find documenting his every move on Instagram, “Everything is blurgh!” he adds. “Like, ‘This is what I had for breakfast!’ I kind off miss a wee bit of mystery.” There’s something defiantly, pleasingly old-school about Neeson, who still believes in the power of the communal cinema experience.

“I get worried about the industry sometimes,” he says, “that people will stop going out to sit in an empty room with strangers and watch something hopefully magical.” Cinema as religion – it’s a compelling idea.

Silence and A Monster Calls both open on January 1.