Suki Waterhouse is currently channelling her French alter-ego, and she's pretty convincing. This week, the actor and musician headed out looking exquisite in a timeless navy suit by Longchamp for a party that the brand was hosting in celebration of its collaboration with art magazine Toiletpaper. It was here that Waterhouse embraced all things Parisian. "It's my French aspirational self," she joked of her finished look. "What shall we call her? Su."

We joined the Daisy Jones & The Six star in her hotel room as she got ready for the starry event, and she opened up about her style heroines (Jane Birkin, Dakota Johnson and Jennifer Lawrence), the music she listens to when getting hyped for the red carpet ("It's always such a mix") and why being alone in her own space is where she feels her most beautiful.

Please talk us through your look – what drew you to this particular outfit?

"I gravitated towards a plain and simple classic navy blue suit. I first saw it in Paris at Longchamp's store; I just put it on and fell in love with it. It feels so perfect when things just fit right and don't need any tailoring, so I could just put this on and be totally ready to go. It's so classic."

How do you decide which brands you want to work with?

"I love working with brands that have a rich legacy and history, particularly those which have a family history such as Longchamp. I have loved meeting everyone, trying to figure out those family dynamics and discovering what they all stand for. To me, it's the most incredibly authentic thing to do as a family; owning a brand that's long-lasting throughout generations."

What makes Longchamp such a great fit for you and your personal style?

"It's elevated – this isn't something I consider myself to be in my day-to-day and definitely need that help, but it's what I like to think of as my chic French alter-ego, where my hair is perfectly tousled and I am wearing clean, ironed trouser suits. It's my French aspirational self. What shall we call her? Su."

How involved do you tend to be with the styling process?

"I'm completely involved. I've been getting myself dressed and going to these sorts of events for quite some time now, but that doesn't mean it can't go wrong. Sometimes, you get carried away and can make a massive error; there are so many bad pictures on the Internet I wish I could erase them forever. I work with stylists, but every single decision and thing that goes on my back has to come from me. Even if it's not on the day, it will be the way you wear a bag or those little touches. The person really changes the outfit, then the mood from hair and make-up is so key as well. I like to pay attention as much as possible."

What kind of fashion makes you feel your most confident?

"If I'm truly feeling my most confident, it's probably something that I can move in, walk and can hold myself well. I find it so interesting with fashion how new eras can come in, and then suddenly something you would never have worn a few years ago, you can't get enough of. You could never have told me that I would be into wearing mini skirts; recently all I want to wear is denim mini skirts, am I 15 again? I guess you just fall in line with what era you find yourself in."

How has your style evolved over the years?

"It's evolved quite dramatically. If I look back at pictures of myself when I was first going out – sadly there is photographic evidence – it was a bit all over the place. I used to wear knee-high socks with heels, but not in a good way. I can track what's gone on over the years by looking at my different outfits. I'd like to say my style is probably in the best place it's ever been currently, just because you get wiser, as going into my 30s I feel a little bit of a shift. You're a little more aware of presentation – I'm not just walking outside my house looking like complete garbage, instead wanting to feel elegant and tuning in to how much that helps me find my place in the world."

What has been your most memorable fashion moment in recent years and why?

"I loved wearing Fendi to the Met Ball a couple of months ago, but my all-time favourite moment has to be my first ever Met; it was years ago, when I wore the most beautiful Burberry pink rose dress made for me. Then I really enjoyed the Daisy Jones & the Six tour as it was so Seventies-inspired and we got to really dress up and have fun, so we had some Fendi looks in there and Stéphane Rolland green dress I wore to the premiere, even though my bum was fairly exposed, it felt great."

Suki Waterhouse at the 2023 Met Gala

Whose style have you always admired and why?

"My mother does a great T-shirt and jeans in the daytime. Jane Birkin and her daughter Lou Doillon who's a musician and actor – everything to do with her, I die. Dakota Johnson always looks really great too. Recently, I've been loving what Jennifer Lawrence is wearing, it's so classy and she's wearing some amazing coats. I really love Alison Mosshart because she just sticks to what she knows and has a great personal uniform. Just French people have the best street style, and English girls too. Anita Pallenberg I always really admired. Pattie Boyd, the way they'd step out at a party in the Sixties was just unbelievable, all the vibrant colours and tiny little dresses. When I get the chance to and it feels appropriate, that's one of my favourite things about fashion is being able to almost transport yourself through the times and lean into it."

What is your ideal getting-ready set-up?

"A big bathroom, access to room service and a good hotel that has decent razors that don't cut your legs up. I've lost count of the number of times I'm usually bleeding before I'm about to head out on the red carpet after an emergency leg shave. Then, of course, good music and a positive team that doesn't freak you out and keeps things calm and collected. Having extra time is always great, it's the worst when you feel like you're rushing and late. Although sometimes it's chic to be late. I love listening to the BeeGees, Led Zeplin, Joni Mitchell for those quiet moments, and The Rolling Stones, it's always such a mix. If I'm feeling a bit anxious and need to get amped up, I'll go for some rap from Rick Ross or something."

When do you feel most beautiful?

"Just with nothing on, being in your own skin. That sounds weird, but it's just about being comfortable. Sometimes, I feel at my best when I'm clean in my joggers, really engrossed in something around the house. Just being in your own space, with nothing else around you and no pressures to look good. Maybe I'm playing guitar or piano, where you're just sitting with yourself and can kind of investigate your own brain. I love that kind of solitude."

Fashion has a reputation for being frivolous, but why does what we wear matter?

"What we wear matters because there's so much history attached to it, you can find out so much through clothes and there's so much significance to what we wear. Although there might be some people who wouldn't admit it, fashion is so important, as it's what we cover our naked bodies with, so those choices are so important. People may say they don't care about clothes, but they do in some way; fashion is about how we want to show up and who we want to be in the world. It's fascinating.

"It's an amazing way to understand one another and bring people together. There are so many implications – both political and cultural – that we don't even realise at the time. Even the fact that I'm wearing this suit, which is usually worn by a man and has been a way to constrict them keeping them uptight. It's cool that we've repurposed it for women to wear, now it's considered sexy and feminine. There are endless things to be fascinated with fashion, even carrying a handbag, it's considered to be related to women providing and carrying a burden. There's psychological meaning to everything we choose and wear."