You can tell a lot about a very famous person by the way she enters a room. Charlotte Gainsbourg, famous since she was a child, slips in quietly, clutching a cup of tea.
By way of hello, she asks the woman seated at the table, the one fiddling with the lip liners included in Charlotte's new make-up collection for Nars, if she might like something hot to drink.
"Did anyone ask if you wanted a coffee?" Charlotte enquires, gently, as though she's afraid of disrupting a cosmetics-induced trance. "Or how about a tea?" With that, she takes her seat, picks up one of the lip pencils, twirls it between her fingers, smiles sidelong and asks, "What do you think?"
I previously wondered whether Charlotte Gainsbourg's anti-diva persona could be a facade, finding it impossible to believe that the daughter of international style icon Jane Birkin and notoriously louche and brilliant singer/songwriter Serge Gainsbourg could really inhabit the world without a hint of pretension.
But all it requires is a few moments in her company to set those doubts aside. Actress, musician, model, fashion muse: in person, Charlotte, 46, carries none of this before her. She's just a woman with mussed hair, in a simple white button-down, drinking tea.
Of course, the difference between drinking tea with Charlotte Gainsbourg and drinking tea with, well, just about anyone else, is that the conversation is peppered with stuff like: "Oh, you know, the process was very simple, I met Fran??ois on a photo shoot, and a few months later, he got in touch to ask if I'd like to make a collection with him." Or, "Those first 10 years with Nicolas at Balenciaga, they were great years."
Fran??ois, naturally, is Fran??ois Nars, the legendary make-up artist and founder of Nars cosmetics. And make no mistake, he's not ringing up every star he slaps a bit of blusher on to ask if she'd like to collaborate with him.
And Nicolas is Nicolas Ghesqui??re, ex-Balenciaga boy genius, now at Louis Vuitton, and Charlotte's great friend.
Which is to say that Charlotte Gainsbourg's average day is distinctly non-average. She's never had to seek the limelight, because it's always found her.
But what does anyone know about Charlotte Gainsbourg? The biography precedes her, and for the most part she chooses not to discuss it; her effortless everyday style - typically Notify jeans and staples from James Perse or 45R - is a form of urban camouflage.
When she dons a challenging Ghesqui??re look, or stars in a film directed by Lars von Trier (notably 2013's Nymphomaniac), or by her long-term partner Yvan Attal, she's assuming a character. Her most direct statements of self have come via music, such as her IRM album, recorded in the wake of her recovery from a brain injury in 2007.
Which is why it makes sense that Charlotte - who admits to not wearing much make-up and having "difficulties" with her skin - would opt to create a collection that resonates emotionally.
"When we started, what I was thinking about was the way we use make-up on films, to enhance the feeling," Charlotte says. Of all the items in her collection, the Multiple Tints are her favourites - one is called Jeanette (her father's pet name for her mother), and two others are named after her daughters.
Other items reflect her minimalist approach to her own look. These are in accord with Charlotte's strategy for sloughing off her various public personae, and dropping back into herself.
"When you play parts for a living, it's nice to be able to go back to something simple and true," she says. "So in my everyday life, I like to be the most 'me'. You know, sneakers and jeans.
"That's why," she goes on, "I've always been uncomfortable with the idea that I'm this 'style icon'. I'm actually rather clumsy and hesitant when it comes to fashion. When I look at someone I think of as a style icon, like Audrey Hepburn, I feel like the aesthetic we associate with her reflects a singular, strong persona. Which I honestly don't think I have."
Given that there are legions of women who'd give their eye-teeth to pull off a "nothing" look with as much aplomb as Charlotte, it's tempting to accuse her of false humility here. But she's plainly sincere when, dropping her customary reserve, she laughs at herself for her shopping foibles, berating herself for "buying too much stuff - things I never wear", and defaulting, as all busy women do, to "winding up wearing the same-old, same-old all the time".
"Which has its advantages," she adds. "I can always count on my children [Ben, Alice and Jo] to bring me back to reality. For one thing, they're always ready to take the piss. They'll tell me if I look ridiculous, if I don't look like myself.
"Consistency and simplicity help me navigate all the things I do, from being on a film set to working on this makeup collection to spending time on the album I'm trying to finish. I can be the same person - and yet, not really. I'm not the same with a film crew as a fashion crew, not the same with my children. "It's always different. But at least the jeans are the same."
Charlotte Gainsbourg's new album Rest will be released in November.