Karla-Simone Spence: 'We don't want to see Black trauma on screen'

But in spite of her lowly status and the horrors she's witnessed, including brutal experiments on her enslaved peers, the fire in her belly still burns bright, a trait which Spence admires greatly: "She's very witty and it's her bravery in that time period [that drew me in]. She says things that would be considered shocking, but she also doesn't go too far. She knows how to tread the line.

"And Frannie's just so human. She makes choices that could annoy people, like anyone does. No one's perfect. To be able to play someone who has so much depth over four episodes, it's an actor's dream."

Frannie is stationed in the Mayfair mansion of George Benham, a celebrated scientist whose respectable exterior belies the barbarism simmering within. Like many of his peers, he's a firm believer in the moral validity of those ghoulish experiments, which were used to bolster the white supremacist cause.

"She's prepared for the worst when it comes to him," says Spence. "She's very closed off and very particular about what she says and does because she's on edge."

But while Frannie's painful backstory and her current predicament are a key part of this narrative – she's accused of double homicide after Benham and his wife Madame Marguerite are found dead – there is beauty and tenderness to be found.

"No doubt you'll be thinking that this is just another one of those slave stories, all sugared over with misery and despair," says Frannie, directly acknowledging audience preconceptions.

In the midst of her darkness is a single source of light: Madame. The pair connect instantly, not only attracted to one another physically but also intellectually, with Frannie and her mistress falling quickly and passionately in love, risks be damned.

"She's never experienced love before," says Spence. "And when she's around Madame, she's able to be closer to her true self. They relate to one another so much. They're like birds trapped in a cage."

Collins's decision to deviate from the familiar 'slave story' beats that we've long been fed was a huge draw for Spence: "We don't really want to see Black trauma on screen. We're multifaceted. We're not a monolith. We love and we cry, and we want to see new stories that aren't entrenched in sadness and pain.

"While Frannie is set in this time period and she was born into slavery, while she can't escape from that, it's a story about her. It is showing all the different parts of her life."

Spence was raised in south-east London but her grandparents were born in Jamaica, which helped her establish an innate familiarity with her character.

"It's my whole life," she says of her heritage. "And reading her story, it just felt really close to me, really close to my heart."

She went on to highlight the rarity of this type of role: "There just aren't many lead parts in period dramas for Black people. I've waited so long to play this kind of character. They don't come by so often for women like me. A three-dimensional Black Jamaican woman in Georgian London is something we haven't seen before."

What's the key to ensuring that this isn't just a trend but an enduring legacy?

"It's about having more writers that are envisioning us as people in a show," she adds. "Having more than one, not just the 'token one'. With open casting, they'll see everyone for a role but I feel like characters are originally written with someone in mind. When it's a character that's written with you in mind, like Frannie, it's just so much easier.

"When she came around, I was just like, 'Wow, I need that.'"

The Confessions of Frannie Langton is airing now on ITVX. Looking for something else to watch? Check out our TV guide or visit our Drama hub for all the latest news.

The latest issue of Radio Times magazine is on sale now – subscribe now. For more from the biggest stars in TV, listen to the Radio Times View From My Sofa podcast.