Sex Education's Mimi Keene and Chinenye Ezeudu on Otis and Ruby, Viv and Jackson, and scene-stealing pet dogs

Keene has played popular Ruby Matthews since the teen comedy-drama's inception, but the next batch of episodes will see her take on a more prominent role as the series explores her background and what lies beneath the character's 'mean girl' exterior. "I was less surprised by her [previously] because she was more sort of one way – she's mean, she’s selfish, it's all about her… that's sort of the vibe," Keene explains. "But when I read this season, she got to open up and you got to see her vulnerable side and see the way that she truly is. The way that she's portrayed herself is sort of like a facade almost until this point.

"I think when you play a character for, like, a couple of years, you build who they are in your mind, and you make a story for them, and their background. So to be able to open that up to the audience was something that I was really excited to do when I read it."

The new season delves into Ruby's difficult family life – it's a recurring theme in Sex Education that characters who might seem like stock types familiar from countless other high school dramas (the jock, the bully, the nerd) reveal themselves to have hidden layers and now it's the turn of Keene's character.

"That was very different," she says of depicting an as-yet-unseen part of Ruby's life. "Being able to show someone's home life gives you way more opportunities to delve into that character. So for me, that was probably one of the most challenging parts, because she's very embarrassed of who she is. Playing someone who's feeling shame and feeling embarrassed is very different to what's come before. She's never been embarrassed before. She's just proud of everything and who she is.

"I don't want to give away too much. But what she goes through in her home life, I think is something that... you don't see it because it's something that people go through at home. That's something that not a lot of people see, [especially] if it's the kind of person that hides themselves, and portrays something that isn't really true. So that was really, really challenging, but very, very good for me this season. I feel very lucky that I got to do it."

Having joined Sex Education in its second season, Chinenye Ezeudu is also getting to play a different side to her character Viv Odusanya this year. A quiz team member who agreed to tutor Jackson Marchetti (Jackson Marchetti) but also ended up supporting Moordale's head boy through a severe bout of anxiety and depression, Ezeudu says that she was shocked by where the new episodes took Viv and she expects fans to have a similar reaction.

"I was surprised how far that would go to succeed and where ambition takes her," she hints. "I think Viv is a surprising character. And if we go beyond surface level with her, she has so much depth. She's going through a lot this season and it really reminds me of when I was at school, trying to figure things out."

As for what's next for Viv and Jackson – Sex Education fandom appears split on whether they should remain friends or couple up – Ezeudu quips, "They get married – episode one! No, I feel this season, it kind of explores the ups and downs of their relationship. Viv found her tribe in Jackson and Jackson found his tribe in Viv but there's a lot of tension this season between them. Ultimately, maybe they're together. maybe they're not, you know?"

Last season did see an unlikely hook-up between Ruby and the show's amateur sex therapist Otis (Asa Butterfield) and though Keene is tight-lipped on whether they'll pair up permanently, a trailer for the third season does seem to hint at their union being more than a one-time thing.

Read more: Sex Education season 3 review: A fun, raunchy and joy-filled ride

"I suppose people are expecting something because of the way last season ended," says Keene. "You've only really seen them having, like, a couple of exchanges – and I won't give away too much, but they're taking it to a slightly different level this season.

"It's very funny to see those two together… I think the best part about it is how they sort of bounce off each other because he's so kind of awkward and polite. And she just says it how it is… but you know, she's not completely dead on the inside either. So that's probably the bit I'm most excited for people to see – the dynamic between the two of them."

The Otis/Ruby pairing has proven popular amongst a contingent of fans, some of whom are even calling for Otis to end up with Keene's character rather than his established love interest Maeve Wiley (Emma Mackey). "I really respect the people who support Ruby even though she's not the easiest to support," says Keene with a smile. "You know, I think they're the people who see through it. They see what she's actually like, so I appreciate those people very much.

"I don't look at it [the fan reaction] too much, but it's nice to hear. I'm glad that people think that it's a good idea. And hopefully they'll be pleased with what they get this season..."

Established relationships aside, both Ezeudu and Keene are hoping to strike up new on-screen partnerships if (or more probably when) Sex Educations returns for a fourth season. "I want to do a scene with Ncuti [Gatwa, who plays Eric]," says Ezeudu. "I haven't done any scenes with him. I would love to work with Gillian [Anderson, who plays Jean Milburn] at some stage. I've not had a scene with her. Ever."

She laughs: "I just think she's really cool. I've seen her in the distance and I’m like, ‘Wow, she’s cool’."

Keene picks Jim Howick as eccentric science teacher Colin Hendricks, citing a scene where Howick's on-set antics led to repeated outbursts of giggling as one of her favourite Sex Education memories. "Ben Taylor, the director, was like, 'Guys, seriously, come on, we've got to get this scene before the sun goes down...' it was so funny. So I did experience it [working with Howick] there but I'd like to experience it more."

It remains to be seen what exactly the future holds for two of Sex Education's most memorable characters – though one other of Keene's long-held wishes has already come true, with her pet dog, Baby, making a cameo appearance in the new season. "I've never been this proud in my life," she says. "I'm a proud mother. I've been trying to get her in since season one – I've been, like, slowly, slowly, bringing her with me every day, letting everyone get to know her…

"She's a star, she is. She's a diva, but she's allowed – she's the one person that's allowed. Now she just needs a red carpet moment."

Sex Education returns to Netflix on Friday 17th November – read our guides to the best series on Netflix and the best movies on Netflix.

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