Joe Wright knows Keira Knightley very well, having directed her in three of her most striking roles - Elizabeth Bennett in Pride and Prejudice, Cecilia Tallis in Atonement, and now the tragic Anna Karenina.
So why does this prized director, who could have his pick of young actresses, keep going back to the same one?
"Keira's grown up as an actress, from 19 when we made the first one (and she earned an Oscar nomination), 22 during Atonement and now 27, and I wanted to bear witness to that," he explains.
"She's deeply intelligent in a nerdy way, dyslexic like me, so she has to make patterns that other people wouldn't necessarily think of, and it makes for extremely intuitive film-making.
"Without Keira, we wouldn't have made this film."
Tim Bevan, one of the big creative brains behind the unstoppable force that is production company Working Title, is equally admiring but also pragmatic...
"It's two things - she's a great actress, but she's also a movie star, and that helps you get films made. She's the complete package, and that makes studio bosses confident, along with Jude Law, Matthew Macfadyen, Aaron..."
Having Knightley on board may have greased the wheels for ANOTHER production of the Russian classic tragic tale, with the actress a shoo-in for her beautiful tragedy of heartbreak, big furs, seduction and despair, but it didn't stop the project having to change shape, once it was decided NOT to film in a big Russian landscape but to bring everything into one stage, which lent a much more self-conscious, theatrical air to proceedings.
Bevan reflects that this change may have helped the film find its niche...
"In a way, it helped us find our raison d'etre, because so many people have had a go at this film. One avenue would have been to out-epic everything - which could have proved costly and futile - another is to do what we've done, a bold visual take.
"Epic doesn't come from landscapes necessarily, it comes from striking images and emotion, and a bit of danger, and we've got that.
It's true of the film that, as Bevan says, after the first ten minutes of adjusting to the stagey feel of the film, with Matthew Macfadyen's Oblonsky having a big swirly barber's shave, you forget and stay busy enough with just the story to occupy you...
"But I think that's true of any film," adds Bevan. "It's about the director making you comfortable, and taking you anywhere he needs to in a cut."
That director is the same Joe Wright who took us to the beaches of Dunkirk for the stunning visual display of the World War II beaches, in a single five-minute shot for Atonement. So why is he now preoccupied with the goings-on of Russian families, each unhappy in their own fashion as Tolstoy told us 140 years ago?
"I read the book several years ago, and it appealed to me," he offers.
"Because I've got to that stage in life too - 40, having babies - and so it all made sense to me. It's basically a family soap, which just happens to take place in a big environment."Anna Karenina is in UK cinemas from Friday 7 September. Watch the trailer below...