Black Mirror: Paapa Essiedu and Anjana Vasan loved the 'unlikely' romance in Demon 79

Watch: Paapa Essiedu and Anjana Vasan discuss Demon 79's unexpected romance.

Paapa Essiedu and Anjana Vasan were surprised by the events of their episode of Black Mirror, Demon 79, and the "unlikely" relationship that develops between their characters, but they also loved it in equal measure they tell Yahoo UK.

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The episode, which is the finale of season 6, follows Nida (Vasan) a shoe shop assistant whose heritage has seen her become subjected to racial microaggressions, such as her boss making her take her lunch break in the basement because a co-worker complained about the smell of her food.

It's there, in the basement, where she inadvertently agrees to a task that puts the survival of humanity at risk, with Essiedu's Gaap acting as her guiding light along the way (sort of).

Warning: This article contains spoilers

Gaap, it turns out, is a demon from hell and Nida is confronted by him when she accidentally bleeds onto a talisman, summoning the creature who informs her she must kill three people by May Day or the world will be consumed by fire and blood. Not exactly the place for romance, one would say, but somehow it works.

"I think that they were unlikely pairing, an unlikely duo that become an unlikely couple," Essiedu shares with Yahoo UK.

"But, in many ways, they're going through a very similar thing. They're both loners within their own slipstream, they're both trying to progress in a world that is not making it easy for them to do so, right?

"And they kind of gel really well with each other even though a lot of, at least to begin with, a lot of Nida's characteristics are about being small or being unnoticed, blending into the background.

"Whereas Gaap starts off looking like an actual demon from the bowels of hell and then ends up with a big afro, angel wings, platform shoes, he's very conspicuous, and I think that just offers us a lot whenever you see the two of them together."

Gaap's look is inspired by Boney M's 1978 performance of Rasputin in Top of the Pops, a look that the demon tells Nida she finds appealing and so will help make her comfortable as they work together while she finds three people to do away with in three days.

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The episode blends its dark subject matter with humour well, with Vasan praising Charlie Brooker and Bisha K. Ali's writing for combining the two with ease.

"Honestly the script was written so well. Bisha and Charlie, they're writing just compliments each other, and I think it was seamless, so the work is there for you, like it's all there in front of you,"she says.

"A lot of it was about finding what it would be like live, because so much of what Nida is going through is reactive. You know, she meets a demon, she feels like she's convinced to do these things, and she's trying to find the moral logic within something unspeakably horrible."

Discussing the relationship between the pair, Essiedu goes on: "I think they need each other. I think they vibe with each other, they gel with each other and I think as they go along through the journey the way that they end up with each other is, I found, really impactful and moving."

Nida chooses to kill people she feels deserves it, such as a pedophile and a man who killed his wife and got away with it, but she is stopped before she can kill a third person.

As a result, humanity is doomed but Gaap offers her the chance to join him in Eternal Oblivion where he has been banished for failing to guide her properly. Nida agrees, and the two walk off holding hands as terror unfolds behind them.

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Of this final moment, Vasan reflects: "It was surprising and lovely, the eternal oblivion [and] how scary that it is [but it] suddenly became this sort of romantic place, and actually a more optimistic place compared to the world that they were leaving behind.

"How much did this world value someone like them, you know? And I just thought it was such an interesting, surprising ending to the story."

Vasan adds that she is keen to know what is next for the characters, saying: "I mean, what is the Eternal Oblivion? We don't know.

"I think there needs to be a spin-off and we discover what the Eternal Oblivion is, there's a version where it's just a dark black room and they're just sat here in two chairs, and it's just nothingness around them, or is it a place of imagination and whatever they want it to be?"

Essiedu has his own ideas of their future together, as he chimes in: "It's Top of the Pops isn't it? It's just like every week for the rest of the time, Top of the Pops."

Black Mirror season 6 is out on Netflix now.

Watch the trailer for Black Mirror.