Manchester By The Sea: Casey Affleck talks about the film, which is already tipped for an Oscar

Manchester By The Sea is the emotional epic on every critic’s radar.

Having premiered near on a year ago at Sundance, the American drama - the third directorial by revered movie-maker Kenneth Lonergan - has already scooped three New York Film Critics Circle wins and is frontrunner in this year’s Oscars race. But up against other grief-stricken contenders - Arrival, Collateral Beauty and A Monster Calls - why has it garnered the biggest buzz?

Proving it’s a marathon, not a sprint, Lonergan is well-versed in the art of cinematic trauma - take his 2000 debut You Can Count On Me, for instance, and 2011 follow-up, the sprawling drama Margaret. But it’s his latest stroke of genius that redefines his trademark intoxicating mix of tragedy and wit.

Manchester By The Sea (co-produced by Matt Damon) tells the story of school janitor Lee Chandler (Casey Affleck), who, after the sudden death of his older brother Joe, is made legal guardian of his teenage nephew (Lucas Hedges).

Returning to his home town in North Shore, Massachusetts, Lee is soon forced to deal with the tragic past that separated him from his wife Randi (Michelle Williams), and the community where he was born.

Affleck, tipped to pick up a haul of gongs for his performance, knew the role would be “a big emotional undertaking”.

“I guess in the way that if you’re someone who jogs a few miles daily and someone says, ‘I want you to go and run a marathon in a few months’, you know it’s going to be quite nerve-racking.

“But you’re a jogger, after all, so what are you doing out there, if not to eventually tackle a marathon? That’s how I felt about it,” explains the 41-year-old actor, known for his enigmatic performances in the likes of older brother Ben’s 2007 directorial Gone Baby Gone, and The Assassination Of Jesse James By The Coward Robert Ford.

Williams, 36, agrees, but states: “It’s really unpleasant; it makes you go to the place that’s the last place on earth you want to go to.” It was a case of taking it day by day when it came to shooting the most demanding scenes. “The days were changing constantly,” explains Affleck, his heavy beard and dishevelled hair masking those familiar features. “But once I was resigned to low-budget, hectic film-making and never knowing exactly what was happening, I put myself completely in that space and just said, ‘Bring it on, whatever we have to do, let’s do it’.

“To go back to my jogger analogy, it’s like if you’re running a marathon and somebody says, ‘Have a breather here, have a drink of water’. It doesn’t feel like: ‘I’m going crazy; am I running or drinking water? I don’t know what I’m doing’. You just drink the water and you thank God for it and you then you go on.”

Williams - whose smaller role meant she would simply take the tram to Boston from New York when needed - confides she found it easier to leave the part “on simmer in my mind”, rather than put it down completely between shoots.

“It’s a little bit there all the time,” she elaborates. “And in some ways, to be able to work on something while you’re running errands, in line at the grocery store, or driving to pick up your kid from school, to just having something to meditate on and prepare for in a kind of inactive sort of way, is actually really pleasant.

“It mixes your real life with your work life,” adds the actress, who is a mum to 11-year-old Matilda, her daughter with the late Heath Ledger.

Dressed in black, and sporting her trademark platinum blonde crop, the petite star is equally honest about the impact such harrowing scenes has.

“You’d get closer to the set and you’d just think, ‘Man, I don’t want to do this day, I hope it starts to hail and then I can go home and not have to do this scene’,” she admits.

“But it turned out everybody else was feeling like that too. It felt like a death march getting to the last scene.”

Yet there was never any hesitation as to whether or not to sign up.

The draw was largely down to Lonergan’s expertise, with Massachusetts-born Affleck stating: “Even if I hated the man, I would do anything he brought to me because his work is so good.

“He’s made three movies and they are all incredible. Nobody else has that track record. He’s at 100 per cent.

“All of his plays are also really beautifully written,” continues the actor, who featured in Lonergan’s West End production of This Is Our Youth in 2002. “[It’s] astonishing how well they work; you laugh, you laugh, you laugh, and in the end you’re crying and you don’t know how it happened!

“Also, because I love him so much and he’s such a good friend, even if the writing wasn’t as good as it is, I would probably do it anyway because I like hanging out with him,” Affleck adds with a grin.

“I’ve waited this long to work with Kenny,” Williams chimes. “[I thought], ‘Whatever it is, I am there’.”

But while she’s no stranger to engrossing herself in demanding roles - her credits also include My Week With Marilyn, Brokeback Mountain and Blue Valentine - the Montana-born star says she makes her professional decisions purely on a “moment-to-moment” basis.

“It’s just what comes to me at the time, but right now I’m working on a movie that’s a musical. There’s lots of singing and dancing; it’s for families and I’m having so much fun,” she reveals.

“I don’t know if it is ever just one thing necessarily. It’s just how it happened to work out.”

Affleck, meanwhile, is planning to return to directing with long-time friend Joaquin Phoenix.

“I found a book that I loved and I had such a good time working with Joaquin [the pair last worked together on 2010 mockumentary I’m Still Here - and it was Phoenix who introduced Affleck to Summer, his sister, who Affleck married and had two sons with before they separated last year].

“We were supposed to do it last summer and just didn’t get together in time. That’s the only danger of working with a close friend,” Affleck admits, flashing a smile. “You never take anything seriously enough and you sit around talking about it endlessly and then the window is gone.

“So we had to kick it down the road; we’re planning to do it later this year.”

Manchester By The Sea opens on Friday, January 13