It's a warm autumn day in London and in a grand hotel overlooking a main thoroughfare in Knightsbridge, one of the capital's poshest postcodes, Kristin Scott Thomas is fiddling with a window latch, letting in some air. "Ah, now it's too noisy," she says as a barrage of sounds tumble into the room, her vowels so crisp and British it's easy to forget that, as a long-time resident of Paris, she spends much of her life speaking perfectly accented French.
"Never mind." She seats herself on a sofa, smoothing her bottle-green jumper and crossing one black-trousered leg over the other. Her nails are painted red; her heels are high and canary yellow. "Let's see how we go, shall we?" she suggests over traffic that's whizzing along, not too obtrusively, several stories below.
First impressions and the Oscar-winning actress, 57, is as upbeat and no-nonsense as Clementine Churchill, the character she plays opposite Gary Oldman in Darkest Hour, a biopic of Winston Churchill directed by Joe Wright of Atonement and Anna Karenina fame (and co-starring Ben Mendelsohn as the King of England).
While Oldman's portrayal of Winston Churchill is a tour de force, from his cigar-puffing, prosthetics-enhanced demeanour to that "We will fight them on the beaches???" speech, Kristin turns in a nuanced performance as his wife, animating a role that might easily have been steam-rollered by Oldman's constant on-screen presence and charisma.
"When Joe first asked me to do this, I said no," she offers, her gaze steady. "They weren't giving Clemmy - me - enough to do. I told him he could get any old person to do this, so he rewrote the part to make it what it is now. I still think there's more to be told about her; she was an amazing woman."
Kristin wears a grey wig over her chestnut crop to portray the elegant Mrs Churchill, a woman with a penchant for self-made millinery who became a prime minister's wife at 53 - four years younger than the actor, a mother-of-three and recent grandmother, is now. "The idea of being a mature woman isn't cool any more," says Kristin with a sigh.
"Because of the way we look at women these days, it's expected that we will dye our hair and try to look younger than we are. Back then, you'd command respect. You'd be thought of as a lady."
Commanding respect, you sense, has never been a problem for this actor. Over the course of 30 years she has carved a dual career in English and French cinema, with iconic roles in Anthony Minghella's The English Patient and Richard Curtis' Four Weddings and a Funeral, while Francophiles hailed her wonderfully contained portrayal of a newly released prisoner in Philippe Claudel's 2008 triumph I've Loved You So Long, and as a wife who ditches her husband for another man in Catherine Corsini's emotive Leaving.
With more than 70 films to her credit, it's inevitable that some will be better than others. She has previously decried the brief post-Four Weddings Hollywood stint that saw her cast as love interest to ageing heart-throbs Robert Redford in The Horse Whisperer and Harrison Ford in Random Hearts ("Of course I wanted to be top of people's lists," she said, "but I thought, 'What is the point of this?' ").
In 2001 she returned to the stage in a French production of Racine's B??r??nice, between movies including the John Lennon biopic Nowhere Boy and Ralph Fiennes' directorial debut The Invisible Woman. She has been treading the boards ever since.
A few years ago she caused a fuss when, in an interview in UK newspaper The Guardian, she declared she was done with films. She was tired, she said, of all the waiting around ("I did a lot of tapestry"), of scripts being rewritten at the last minute (except, perhaps, when they flesh out characters such as Clementine Churchill), of using her actorly cachet to prop up otherwise flimsy productions.
She spoke of her wish to direct an adaptation of Elizabeth Jane Howard's The Sea Change, a 1959 literary novel that asks fundamental questions about love and its vagaries.
"People do love [creating] a drama. But yeah, back then I didn't want to be doing films. I'd been doing some plays here in London," she says, referring to Betrayal and Old Times by Harold Pinter, and the title role in Sophocles' Electra. "I didn't do a film for four years. Then [British director] Sally Potter sent me the script of The Party and I couldn't resist."
The Party, released this year, is a satire about politics and love in which Kristin plays a newly appointed government minister celebrating her promotion with a dinner. It was shot over 13 days with a star-studded cast including Patricia Clarkson, Cillian Murphy and Timothy Spall. "It was totally mad, completely brilliant. A real ensemble piece, the kind of thing I love doing." She flashes a smile. "It wasn't just me being wheeled in to be grand and make withering remarks."
These days, Kristin is enjoying getting older. Emboldened, perhaps, by the damehood she received from the Queen in 2015 and the Officer of the Legion of Honour bestowed that same year by the then French president, Fran??ois Hollande, not to mention a clutch of best actress gongs and nominations for roles on screen and stage, she is busy doing what she wants. This sometimes means not doing much at all - a self-confessed "potterer and big waste-oftimer", she enjoys looking at art, gardens and architecture. Oh, and reading.
For a long while she felt displaced, sort of existentially homeless, what with being English by birth (she grew up in Dorset, one of three girls born to a homemaker and Royal Navy pilot who died in an accident when Kristin was five) but having lived in France since the age of 19 and made a family there (she divorced her husband, obstetrician Fran??ois Olivennes, in 2008). And while she's spoken, too, of the invisibility that tends to come with middle age, she's feeling more grounded after her 29-year-old daughter Hannah, a journalist, gave birth to a baby girl in June.
"This is all very personal." She pauses. "But let's go. I've recently become a grandmother and understand the order of things; everything has fallen into place. It's an extraordinary experience, looking down on this tiny little baby which is looking up at you and there are two things on its face: love and trust."
Her green eyes crinkle at the corners. "So I'm feeling fine about the invisibility thing. Though on the other hand I still really want to kick people sometimes." She cups her hands around her mouth. "Er, hello!" she mock yells. "I think I was in the queue before you!"
As to whether she has finally come down on one side of the Channel or the other, she no longer seems concerned: "Oh, I'm still chopping and changing," she says breezily.
She first decamped to France to work as an au pair after a teacher at her London drama school told her she'd never make it as an actor, "but the first English job I got was to play Lady Brenda in [1988's] A Handful of Dust, which is the most English thing you could get. It's been a huge advantage, being able to step back and see things at a distance."
Her first English-speaking role, however, saw her playing a French heiress opposite the rock star Prince in his widely panned 1986 vanity project Under the Cherry Moon. She was 26, fresh from studying theatre in Paris and rumour has it that Prince was so dazzled by her beauty that he cast her as his love interest on the spot. "He was a genius, fascinating and slightly odd, as geniuses are," she says. "I will never forget that he gave me my first job, my first chance."
With her cut-glass cheekbones and ability to convey every emotion from infinite sadness to haughty disdain with a glance or a raised eyebrow, it is easy to see why Kristin has very often stolen the spotlight, even in smaller supporting roles. And while the vagaries of her love life are off-limits - she has briefly dated Arpad Busson, Elle Macpherson's ex - she has an openness and warmth in person that doesn't always come across in her roles, though her joy in playing the upbeat Clementine Churchill is palpable.
"Because of the great knowledge we have of her, she was a character I could approach from the outside in," she says. "This was a woman who was so chic and wonderful, with this extraordinary style. She used to work in a hat shop, so she'd make these confections that were similar to the turbans and things worn by women in the factories, who were making tremendous sacrifices"
"She'd wear a fur coat and paisley head scarf to go and visit a bombsite with her husband, who was six inches shorter than her. They had a very loving, very volatile relationship, and Gary is just so extraordinary in the role. We had such a laugh on set; you'd have Winston Churchill sitting there, then suddenly Gary would pipe up with something unexpected and hilarious."
While there is a lot more to be told about Clementine Churchill - and Kristin would happily reprise the role in a dedicated biopic - the opportunity to play a woman who looked and acted her age was part of the appeal. "Things are changing slowly in film," she says. "There are lots more things being written for mature women, and about time; maybe we've been ignored because we are at our most powerful at this age.
"Our most powerful," she reiterates. smiling. "Which is exciting, isn't it?"
Darkest Hour opens on January 11.