Kristin Scott Thomas on the pain behind "My Mother's Wedding"

She may be Dame Kristin Scott Thomas, but you're just as likely to find her living in Paris as you might in London. "My blood is English, but my culture is French," she said.

There is a duality about her. She can be as heartwarming in English ("Darkest Hour") as she can be heartwrenching in French ("I've Loved You So Long"). Many of her foreign films have been showcased at the Cine Lumiere, a French art house in London. "A little slice of Paris," she said.

It's convenient, now that she's back in London, playing the deputy director of MI5 in the Apple TV+ series "Slow Horses."

A chilly, stiff upper-lip has often been a calling card for Thomas – too stiff, she admits, early on: "I think it was Sydney Pollock – or it might have been Robert Redford, take your pick," she laughed. "One of them said to me, 'You know, you have to be generous. Forget what you're trying to defend. Forget trying to hide. Be more generous.' And I'm not sure I really understood what he meant by that. He just planted a seed, and then I was able to kind of unzip a bit more."

And she about to unzip even more, creatively digging into something intensely personal in her past. She said, "When I was five, my father was killed, and my mother remarried. And tragically, he was killed five years later. And I know that a lot of the time when I was a younger woman, I had this feeling of something missing, this piece of my puzzle missing having grown up with only one parent."

Both had been pilots in the Royal Navy's Fleet Air Arm; both were lost in remarkably similar training accidents; and both left a hole that had her climbing out into her imagination. When she was a little girl she wrote and illustrated stories: "A mommy and a daddy and two children, just doing ordinary things, like going away on holiday and things like that" – a family experience she never knew.

The memories of her dad were incomplete, fuzzy, like sketches she played out in her head. But those images became the seeds for what grew into a screenplay, and then came to life as the first movie she's ever directed: "My Mother's Wedding."

It garnered an all-star cast: Scarlett Johansson, Sienna Miller and Emily Beecham play Thomas' daughters who are each struggling in different ways with the loss of a father or stepfather, just as their mother prepares to marry again.

To watch a trailer for "My Mother's Wedding" click on the video player below:

Thomas has already done movie weddings, of course, as in "Four Weddings and a Funeral." Early on, she had a sarcastic confidence about her. She didn't have the most lines in that 1994 film, but in brevity she was brilliant:

That demeanor might have been a surprise to those who knew her when she was bouncing around Royal Naval bases, a bit of a wallflower as a child, even into adulthood. "I was excruciatingly shy," she said. "I don't know when it changed, to be honest."

She's hardly shy anymore, if her character in "Fleabag" is any indication. Perhaps it's fitting she was discovered by another admittedly shy success story, Prince. You'd think that would make her a pretty cool mom (she has three children with her first husband), but it turns out … not so much.

"I hadn't watched it with them, but as I was leaving my teenage children alone one evening, and they were having pizza and a friend 'round, I said, 'Watch "Under the Cherry Moon," it's on the telly! Come on, it'll be fun!' And when I got back, they weren't actually very polite about it."

She has more than made up for it, later starring opposite Robert Redford ("The Horse Whisperer"), Harrison Ford ("Random Hearts"), and Tom Cruise ("Mission: Impossible").

"I'm so proud to be in 'Mission: Impossible,' I cannot even get over it!" she said. "I'm in this thing, which is this enormous monster, and you know, these kids, they have no idea about 'Gosford Park.' They have no idea about 'Four Weddings,' but they've all seen 'Mission: Impossible'! And they have no idea I speak French or do all these other kind of slightly murkier films in France, you know?"

And then, of course, there was "The English Patient," which earned her an Academy Award nomination for best actress. "It's quite moving actually, when you see yourself at sort of 30 acting your socks off," she said.

Another place she acted her socks off is at the Royal Court Theatre, where she won an Olivier Award for her performance in "The Seagull," a role she later took to Broadway. "New York audiences, when they are enjoying themselves, I mean it's electric – you can really, really feel it," she said.

And London audiences? "We are much more kind of passive, perhaps. Reserved. Of course we are!" she laughed.

But even while talking at the Royal Court, she found herself thinking about her film. As intimate as the stage may be, for her, "My Mother's Wedding" is more so. "I love working on stage, as you can probably tell. I really, really love it. But the joy and satisfaction and exhaustion that comes from filmmaking when you are being a director, that is not far off. Pretty good. It's just extraordinary."

At 65, and now a grandmother, she's working as hard as ever, not taking a lot of time to smell the roses per se, but she'll surely stop for someone who has a kind word or two: "A lady came up to me the other day and said, 'I know you hate this, but I just wanted to say...' and I said, 'I don't hate this at all! Keep it coming!'"

WEB EXCLUSIVE: Extended interview - Kristin Scott Thomas:

For more info:

• "My Mother's Wedding" opens in theaters August 8
• "Slow Horses" on Apple TV+

Story produced by Sari Aviv. Editor: Steven Tyler.