There’s nothing more intimidating than the incredible woman beside you at pilates who endlessly holds a bridge – with the added leg raise! – when everyone else is melting into the recovery pose. Well, Mimi Keene is that incredible woman.

I witness Keene at the photoshoot for this very feature, body contorted into a number of positions I’m sure I couldn’t manage even after an intensive six-month yoga retreat. She’s comfortably holding increasingly demanding poses without even a solitary bead of sweat forming. All this after partying at the BAFTAs the night before. And she looks phenomenal doing it.

Oh, I forgot to mention she’s also wearing baby-blue tights and a matching top – the creative vision of stylist, Oisín Boyd. Most people would look like they were sporting a Smurf fancy dress outfit in something like that. Not Mimi Keene. This girl can make anything look beautiful.  

Which is just as well, because looking glamorous often comes with her job description – including her latest role in the BBC’s adaptation of Agatha Christie’s Towards Zero. In true Crime Club style, it starts in a decadent dining room, with tentative looks, suggestive eyebrow raises, and a pan around the table of our suspects – including Keene’s character, Kay Strange. 

Kay is a socialite recently married to tennis star Neville Strange (Oliver Jackson-Cohen). She’s spending the summer with him at his childhood home – the estate of his aunt, Lady Tressilian (Anjelica Huston). Neville invites his ex-wife Audrey (Ella Lily Hyland) along, too. What could possibly go wrong? Locked away in their coastal bolt-hole, tides and emotions turn in tandem, our trust in the building cast of suspects wavering as quickly as the weather changes.

Mimi Keene

Along with the serving staff, Keene’s character becomes embroiled in a high-class world of untold histories, lies, seduction and deception over the course of their stay at the stately home. Keene shares that elements of the shoot became “accidental method”. She explains: “It’s not that usual to film something inside the place where it’s actually set. I felt very immersed in the story – I was living in Agatha Christie’s world.” And when the cameras cut? Fortunately there were fewer furtive glances: “It was such a good buzz and good vibes when we weren’t filming.” 

As a lover of closed-room mystery, I wanted to know what it was like to actually be in one. Did the tension feel real? Did she find it hard not to accidentally give away the plot because she knew who the murderer was? She says the tension in the room did build; it’s smokey, strained, temperatures quite literally rising (lighting rigs will do that to a set). As for the notion of who the murderer was? Well, forgetfulness was her friend. “I usually read the script the whole way through once, and then only my parts. I don’t have a great memory, so in this situation, that was very useful,” she laughs.

Despite having seen these actors in modern-day dramas, not an inch of me believed they had lived in an era other than this one. The set and costumes are dazzlingly beautiful and believable. I ask about her character of Kay. She tells me about how she uses fashion as both an attractor and as a guise. The show sees Keene sporting outfits which, for the time, would have been considered especially avant-garde. She enjoyed time-hopping to the 1930s, her favourite part of the job playing dress-up: “I loved it – and I would love to do it again.”

Her looks on the show include a “fashion-forward” red bikini, a bold blue jumpsuit, and some seriously impressive hats. She sports a surprisingly fetching short wig throughout the show: “I was worried at first that they were going to have to chop a lot of my hair off; I don’t know how the hair and make-up team made it fit.”

Speaking of hair and make-up, even they play a crucial role in the show. Keene recounts the intricate details considered to help heighten the drama: “I would have blusher on the days where she was happy,” she says. “When it was gloomy vibes, or you know… murder vibes,” she raises an eyebrow and gestures a blocking motion with her hands: “No blush!”

So, ostentatious wardrobe? Tick. Bold beautification? Tick. “Touch wood it carries on forever, but so far in my career, I have been given amazing costumes. There must be some costume angels looking down on me somewhere, I think.”

Mimi Keene

Keene is clearly in her element – as she was with the role that catapulted her career: Ruby Matthews in Sex Education. The iconic coming-of-age Netflix show garnered 40m viewers within its first month – and went on to four hugely successful seasons, launching many a career in its wake.

I worry she’s bored of chatting about it: “Oh, I love talking about it,” Keene beams. “It’s definitely changed my life – and certainly shaped who I am today.”

The series, agog with love, lube and laughter, deals accessibly but humorously with myriad taboo topics. With garish but glamorous costumes, goofy characters, and great performances, it’s a feel-good lesson in finding yourself – and the very embodiment of binge-worthy TV. I chat to Keene about the topics of sexuality and self-exploration that arise in the show: “They are serious things, but it’s done in a way that is fun and enjoyable at the same time.”

Keene’s character, Ruby, a stereotypical popular girl, softens over the show’s four seasons, becoming a major love interest to protagonist Otis (Asa Butterfield). The show has been quite the phenomenon; the devotion from viewers palpable. We discuss the public reaction: “It’s make-believe, it’s not real – but people’s reactions to it are,” she says. “People are touched so much by it that they want to open up to me.” 

Keene is often stopped in the street by strangers who confess deeply personal information about their sex lives or sense of self. “The show has resulted in a serious rise in hugs with strangers,” she laughs. “It is quite humbling and very emotional.”

Mimi Keene

I ask Keene to cast her mind back to the start, before the streamer success it is today. She didn’t think much about its potential but loved the story. “I read so many scripts at that time. But when I read the script for Sex Ed, I remember thinking ‘I need the next episode.’” This one hit different. “It didn’t feel like work,” she says. “It was so good. I wanted to keep reading.”

The in-vogue fashionista is only one side of Keene’s coin. The other is a bum bag-laden dog walker in waterproofs and wellies, the proud owner of four dogs and a cat. Her chihuahua Baby gets top billing; she also starred in Sex Education. “She’s very small, very easy, and sleeps most of the day.” Keene started bringing her to set in season one. The cast and crew enjoyed having a fluffy friend on site – so much so, she became part of the cast. (Playing herself, naturally.)

The canine cameos were the genius of director, Ben Taylor, who wanted to take the natural chemistry he’d seen of Keene with Baby in her trailer and use it to heighten comedy-drama.

Any conversation about Sex Education must also include Gillian Anderson. Before I can finish my question, Keene interjects: “Oh, I love her; she’s so brilliant!” I talk about recently reading Anderson’s book, Want: a rousing call to eradicate shame through sharing varied sexual fantasies sent in from anonymous women across the world. In the book’s introduction, Anderson writes how playing Sex Education’s therapist Dr Jean Milburn helped her lean into conversations she’d previously shied away from. Keene hasn’t read it (yet) but it’s on her list.

I wonder if, similar to Anderson, being in shag-tastic Sex Ed has given her anything akin to a sexual awakening or personal growth arc. “Oh yes, definitely! It made me more open to trying new things,” she says. Seeing my eyes widen thinking I’ve got some juicy plot for the next Eyes Wide Shut, she’s quick to highlight that she’s not specifically talking about sex or her sexuality. She talks about how the show impacted her more broadly as a person. “From just the smallest to the largest things, it’s changed my life in a whole lot of new ways.”

Mimi Keene

She mentions reading more books and taking skiing and horse-riding lessons. She specifically talks at length about the shift in her personal style, becoming bolder in her fashion choices: “My wardrobe has massively changed and expanded since playing Ruby.” She talks about shopping for unisex clothes and experimenting with gendered designs.

A pocket-rocket at just over five foot two, she is becoming more inventive: “I just find the designs I like in the menswear sections; I like things quite baggy but then have them tailored to fit me.” Alongside the physical clothes, and the new hobbies, she mentions feeling more self-assured and being comfortable when talking about her feelings. 

Not that she comes from a repressed background in the first place. Keene is from a large family. (Her Irish mother is one of eight). “We’ve always been very open about things in our family. Nothing was ever embarrassing.” And while it doesn’t appear to be the overly therapised speak of Dr Jean Milburn and Otis, her family are open-minded, unwaveringly loyal and receptive: “All topics are always on the table; I grew up never nervous to speak about anything.”

She glowingly recalls how healthy it was to have a supportive family that she describes as “very special and unique”. 

“Confidence is always something you struggle to find as you’re growing up, but having a supportive family who are open…” She pauses and smiles. “My grandmother never saw any barriers for us. She would always say, ‘You can have the absolute best’: that’s very much the ethos of our family. There is no ceiling.”

Mimi Keene

Her mother played a role in guiding her toward the screen, though never in a forceful way. After missing out on a place at the grammar school her parents had hoped for, Keene enrolled in stage school instead. “I don’t test well, OK!” she declares, laughing. (Maybe so – but no doubt she screen tests exceptionally well.) “My mum was horrified. I don’t think she’s ever been more distressed than me not getting into that school. Honestly, I think she would have rather home-schooled me.”

Her mum, distraught after the failed entrance exam, immediately started asking questions about other options. The school told her that Mimi had been listed on a gifted and talented register for singing and dancing. The family began researching drama and stage schools as a result.

It was clear from a young age Keene had something people were drawn to. After primary school summer holidays filled with open weeks, drama clubs and preparing pieces of singing and dancing, she auditioned and got into every stage school she applied for. She recalls her family’s reaction: “We knew you had something but you were just in the wrong place”.

She speaks fondly of her time at Italia Conti: “It was a really great experience that’s made me who I am today” and it was from there she progressed to a regular role as Cindy in Eastenders. While I’m sure for a young girl, a lot of the processes and pressures of auditions were taxing, Keene is jovial about it. “Sometimes I believe things happen that seem like the worst thing in the world but they lead you to do something that’s life-changing.”

And life is constantly changing for Keene. We talked ahead of her first of two photo shoots that week. That’s before the upcoming show’s screening as well as a BBC Breakfast appearance but after a BAFTA after-party. I’m tired just thinking about it – and frankly exhausted after witnessing those 12-minute bridge holds.

So, what’s she working on now? She offers the classic actor’s response: she’s working on something, though details are under wraps. What she can say is that she’d be thrilled to keep embracing outlandish wardrobes and flamboyant fits.

I’m intrigued to see what’s next, but one thing’s certain – whatever lies ahead, she’ll look effortless while she does it. 

Towards Zero airs weekly this March on Sunday at 9pm and is available on BBC iPlayer.