Miller was named best director at Cannes, where had its world premiere. The winner of the movie-of-the year accolade at the AFI Awards, also received five Oscar nominations - including best director, and lead actor for Carell - but didn't win any.

Miller's vision involved Carell needing to look as well as act like the real du Pont. To transform into the billionaire heir to the du Pont chemical fortune, a task that included application of a beak-like nose, receding and greying hairline, false teeth and pale complexion, he had to arrive three hours before the rest of the cast. That separated him from the others, which fed into the undercurrents of the movie.

"I felt that my way into him was the sadness that seemed to permeate his life. I think that's what was on my mind more than anything," Carell says. "Here was a guy who didn't stand a chance, in a way, because of his upbringing and because of the other problems he had, mentally and emotionally. It just added up to tragedy for him and for those around him."

One of those caught in the agonising undertow was Mark Schultz, who was on set during part of the production and who tells his story in "I can only imagine how strange and emotional it must have been for him" to witness the director's representation of his life, Carell says.

In conversations with Schultz, "I didn't get into minutiae of du Pont with Mark," Carell says, "but his [du Pont's] demeanour, I think, was something I was trying to pinpoint, his outward appearance and the way in which people responded to him. He was off-putting.

"He was someone who didn't seem to be very comfortable in his own skin and I think that was unsettling for people around him … He … did things that people didn't quite understand or no logic could be made of much of his behaviour, and Mark helped me with that."

Du Pont also was front and centre in a laudatory film he commissioned about himself, and the documentary maker in , David Bennett, did the actual filming. "He was asking the same questions that he asked of Mark and Dave and of John. He was an added layer of gravitas," Carell says. "All the way through, Bennett was able to have the real participants there, either acting as advisers or being included in scenes. It was important to him to fold in a sense of reality to it."

The cast includes Vanessa Redgrave as du Pont's mother, a horsewoman who disapproves of her son's interest in wrestling. "A low sport," she calls it. It's a sport du Pont aspired to master but failed. When Carell - who played ice hockey when he was younger - had to execute some moves as du Pont, wrestling co-ordinator John Guira told him he was too proficient and needed to, essentially, "dumb it down" a bit.

Acting opposite Redgrave was exhilarating and terrifying for the actor, and it didn't help that before Carell met the British stage and screen legend, he recalls, Miller said something like: "She will eat you alive if she chooses to."

In retrospect, the actor says: "I think that there was a method to his madness in telling me that. I definitely went into those scenes, and meeting her for the first time, back on my heels. I was trepidatious about what kind of force she would bring to that character. But working with her was, it ended up being, I don't know if fun is the right word, but exciting and incredibly gratifying.

"She's so remarkably good and very present and very supportive and giving as an actor, and she's a great improviser … She was incredibly nice. She was exactly the opposite of 'She will eat you alive'."

Nevertheless, the movie's ominous tone and sense of dread were reflected in the mood on the set.

"Shooting this movie was very different from anything I've ever done," Carell says. "It certainly wasn't a lighthearted set. There was nothing extraneous. It certainly wasn't a very social place to be. It was incredibly focused on just doing the work. I think for all of us, it took some effort to put ourselves in that place for that period of time."

Although the three leads now enjoy a friendly rapport, that wasn't the case when they were in character. Miller later told them that every time a scene ended, Carell and Tatum would immediately turn away from each other with no hint of warmth or affection.

"And that's just where we were at the time. What's so funny now is we love being around each other. He's such a good guy, but it was just a different kind of experience when we were there in Pittsburgh."

As for the calamitous turn in the movie, Carell says it's "shocking but it's not surprising. It's something that, when looking back across the rest of the film seemed inevitable, but at the same time it does make you jump."

Or, as the director has said, the story is funny and then it's not and then it's not at all.