Hollywood actor Casey Affleck has said filming his Bafta-nominated performance in Manchester By The Sea was "an emotional marathon".
Casey, who has already won a Golden Globe for the role, is considered a frontrunner in the race for the best actor Oscar ahead of the nominations announcement on January 24.
His role as a closed-off janitor forced to take care of his teenage nephew in Kenneth Lonergan's film about grief and survival has already garnered him critical praise as well as awards success, but he said it came at a price.
He told the Press Association: "I knew it was going to be a big emotional undertaking, in the way that if you're someone who jogs daily, a few miles here and there, and someone says 'I want you to run a marathon in a couple of months', you know it's going to be quite an undertaking but, I mean, you're a jogger after all, so what are you doing out there if it's not to eventually tackle a marathon?"
Casey previously tackled Kenneth's work when he starred with his friend Matt Damon, a producer on the film, and future wife Summer Phoenix in Kenneth's play This Is Our Youth in London in 2002.
He said of the playwright: "Even if I hated the man I would probably do anything that he brought to me because his work is so good.
"He's at 100%, all of the plays are really beautifully written, they are astonishing how they work so well. You laugh and laugh and then you're crying and you don't know how that happened.
"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 do it anyway because I like to hang out with him."
Casey will soon return to directing to helm an adaptation of Robert Olmstead's novel Far Bright Star, starring his friend Joaquin Phoenix, whom he directed in spoof documentary I'm Still Here.
He said: "I had found a book that I loved and I thought about who could do it.
"I had such a good time working with Joaquin and he's been my friend since I was 18, we lived together, and I think he's one of the best so it was a no-brainer.
"I thought 'Let's just do it with him'. We were supposed to do it last summer but we just didn't get together in time.
"That's the only danger when working with a close friend is you never take anything seriously enough, you sit around talking about it endlessly and then the window is gone.
"We had to kick it down the road and we are planning to do it later this year."
Manchester By The Sea, also starring Michelle Williams, is released in UK cinemas on Friday.