At the beginning of 2019, Ncuti Gatwa had fewer than 1,000 followers on Instagram. He had filmed Sex Education the previous summer, and by January, it was ready for the world to see. Though it starred big names – Gillian Anderson, Asa Butterfield – on paper the show sounded more like a cult oddity than a smash hit. Butterfield played Otis, a secondary-school student turned sex therapist for his peers in a gaudy world that sat between a John Hughes movie and a Just Seventeen problem page. Gatwa starred as Eric Effiong, Otis’s best friend. Netflix had flown the cast to New York to promote Sex Education, which was released when Gatwa was on the return flight – and his character was a huge hit. When he landed at Heathrow, Gatwa turned on his phone. In the space of several hours, his follower count had gone up… by a couple of hundred thousand.

“It definitely felt exposing,” Gatwa says. He’s sitting in a café in Soho, almost exactly a year after the show changed his life so suddenly. At 27, he is a decade older than Eric, and less flamboyant, though he shares the character’s ebullience. He sounds different, too – his own accent roams Scotland, Rwanda and Tottenham, where he now lives, and his broad laugh ripples across the busy lunchtime crowd.

“I remember the next day, me, Emma [Mackey, who plays Maeve in the show] and Aimee [Lou Wood, who is Aimee] went to Lush, and we were buying our soaps. And our scrubs. I love Lush,” he says, hamming it up, speaking directly into my dictaphone. “Emma said: ‘Ncuti, we have to go.’ Behind her, I saw, not a frenzy, but a group of people forming. We had been spotted.” They felt it best to do a runner. “It was an odd experience,” he smiles.

Nobody quite seemed to anticipate just how big Sex Education would be. Dealing with the sexual hang-ups of teenagers and adults, it was both sensitive and crude, timeless and timely, funny and sweet, and managed to appeal far beyond any youth audience. As Eric, Gatwa became a magnet for viewers’ empathy and affection. He was an out, proud and loud gay teenager, whose Ghanian-Nigerian family were worried for his wellbeing. While he experienced self-doubt and rejection, in the end he triumphantly embraced who he was, in the most heartwarming prom scene since Lindsay Lohan snapped the tiara in Mean Girls.

Facebook Twitter Pinterest School daze: In Sex Education. Photograph: Sam Taylor/Netflix

Netflix’s approach to containing spoilers is notoriously strict – “There’s a Netflix assassin right there,” jokes Gatwa, glancing sideways – but, of course, Eric will be back for season two, and given that the first ended with him finding unexpected romance, anticipation for what comes next is high. “In season one, Eric shows how resilient he is, and that resonates with how resilient a lot of people have to be, especially people who are marginalised in this society.”

My character resonates with how resilient a lot of marginalised people have to be

As a gay man and a black man, Eric is “a minority within a minority, so that’s doubly hard”. Gatwa particularly loves the relationship Eric has with his father, who quietly accepts his son’s homosexuality while being cautious about what that will mean for his life. “I felt, perhaps, if you are from that culture and that background, and are having a situation where you’ve got somebody gay or LGBTQIA+ in your family, and you’re struggling with it, you can watch the show and be like: ‘It’s fine to love and embrace my child.’”

Eric is from a Ghanian-Nigerian family; Gatwa’s family is Rwandan. But they share a religious upbringing. “Within church communities, within black communities, and within black church communities, gossip is thy friend. Gossip will be thy friend!” He slaps his hands on the table and slips into an impression of women in church: “Did you see what sister Ama’s son has done?” “What! And she accepted it! Can you imagine?” “You know I’m not one to gossip…” Gossip, he says, is everything. “So a lot of times in black communities, people are scared – it’s not what they are feeling towards their child, but what aunties are gonna say, what uncles are gonna say.” Eric’s father loves and embraces his son for who he is. “He’s just scared for the world his son is going to inhabit, and that is very human.”

Every day, Gatwa receives a message from someone who tells him that Eric’s experience mirrors their own. He got a DM two days ago that moved him to tears. “This guy, his English was broken, but I got what he was saying. He said, whenever I watch the dance, when you and Otis dance at the end, I can escape my world for 15 minutes. He said, I can go to my dreams.” Gatwa’s eyes begin to water. “It was just really beautiful.”

Facebook Twitter Pinterest ‘They will fall in love with me sooner or later’: Ncuti Gatwa wears blazer by Bottega Veneta, shirt and trousers by Louis Vuitton. Photograph: Dean Chalkley/The Observer

How much of Eric’s story resembles his own? “There are definitely parallels. I related to his sense of isolation, growing up. There’s not many people that look like me in Scotland.” When he was a toddler, Gatwa and his family moved from Rwanda as refugees, fleeing the genocide. He grew up in Oxgangs and Fife, and in a recent BBC documentary, Black and Scottish, talked about being bullied at secondary school in Dunfermline, where new classmates set up a racist Facebook page about him.

It sounds awful. “It wasn’t pleasant,” he shrugs, “but it wasn’t actually horrendous.” He looks mischievous. “Do I want to say this? Yeah, why not… it didn’t really bother me that much because I knew.” He is chuckling. “I was like, you can’t know me and not like me. I was actually quite confused! I was like, what? These people don’t like me? I was like, that’s never happened before.” The laugh blooms into a full-blown guffaw. “So I was like, OK, fine. I’m just going to carry on being myself and they’re going to fall in love with me sooner or later. And they did.”

In the end, he became friends with the boys who set up the page. “It was really a good lesson to me about the difference between hate and ignorance. Obviously their behaviour was inexcusable. But at the same time, I was the first black person that they probably saw in real life.”

Did they talk about it afterwards? “They apologised profusely. Sorry is only a word, isn’t it, but their actions spoke more than that. It wasn’t that horrendous. My mum really toughened me up, as well. I grew up watching her move to this country with three kids on her back. She couldn’t speak the language, didn’t know the culture, no money, no nothing – and she raised all three of us. As cheesy as it sounds, I’ve been watching strength from young. My mum has dealt with so much shit.”

As a child, Gatwa was always lively, but he existed between two worlds. At home, he was quiet, shy and dedicated to his Bible studies. “Outside the house, I was a live wire,” he laughs. “I was a wild teenager.” He won’t be drawn on details, but reels off a greatest hits of teenage rebellion: “Drinking, smoking, being in places you shouldn’t have been. Sneaking out of my house. Ah Mum, you don’t know that one! But I’m nice now.”

He didn’t want to be an actor as a kid, partly because he didn’t even know it was a possibility, but drama was the only subject he enjoyed and, often, it was the only class he’d show up for. “The rest, I was, like, bye! Who needs to know Pythagoras’s theorem?” Two teachers saw his potential and planted the seed of drama school, and he applied for, and got in to, the Royal Conservatoire of Scotland. “I think they were quite excited to have a black Scottish actor. Who knew that was a thing?”

Facebook Twitter Pinterest In the spotlight: with model Charli Howard and castmates Aimee Lou Wood and Emma Mackey. Photograph: David M Benett/Getty Images

Given that he is classically trained, it only feels right to ask him about one of Eric’s more demanding scenes in Sex Education. How do you prepare to publicly fellate a banana? He laughs. “First and foremost, at drama school it gets drilled into you that you say yes to anything. If they say, can you tap-dance with a monkey on your head in your audition, you say yes.” He was shown a YouTube clip of a similar act, and asked to provide something in that ball park.

I won’t lie. With the banana in my mouth, I was thinking, Oh my God…

“I’m not gonna lie. When I was there, the banana in my mouth, I was thinking, ‘Oh my God, three years studying Jacques Lecoq at the Royal Conservatoire of Scotland…’” Somehow, he resists a Coq gag. “On set, every single day was another madness. Every single day, someone is getting wanked off in a car, someone’s sucking off someone’s dad. ‘Oh, what are you doing today?’ ‘Oh just having my third wank of the day.’ That was the nature of the show.”

We’re laughing, but frankness is part of the series’ charm, and the openness about sex and identity speaks to the generation it depicts. “Teenagers now are so progressive,” Gatwa agrees. “I live with my best friend and his mum, who runs a salon in Tottenham and I’m there all the time. Whenever the young boys come in to get their trims, the conversations they have, they’re like, ‘Ah Mum, they’re non-binary, you can’t call them ‘him’. It rolls off the tongue. It’s amazing. That’s the generation that’s going to save the world.”

It isn’t just kids who come up to him in the street. He was at a station recently when a woman and her granddaughter stopped him. “The nan was the effusive one. She said: ‘I wish I had a show like that when I was young, I thought you were brilliant.’ And the granddaughter was just looking at me, like…” He pulls a bored, distant, unimpressed face.

Facebook Twitter Pinterest ‘I’m Scottish and Rwandan. I love that I come from both those places’: Ncuti Gatwa wears Alexander McQueen. Photograph: Dean Chalkley/The Observer

Do people expect him to be Eric? For the first time, he looks a little sad. “Yeah,” he says, softly. “There’s good days with it, and bad days with it. It’s fine, and it’s not fine. But what do I expect people to think? It’s the only role the world has seen me in.” He graduated from drama school in 2013 and until Sex Education, mostly did theatre, though I remind him of a stint as a policeman in the 2015 Scottish drama Stonemouth, and he howls. “People forget about that pivotal role in my career. Really changed things, that one. My mum said I looked like a baby strippergram. Dougie the cop! He will live in my heart forever.”

Gatwa says he gets it. Like Eric, he is a chatterbox. “The thing is, Eric is 16, so he doesn’t need coffee, does he? I will need a coffee at times. Every time you see me I’m not gonna be bubbly and smiley.” Being stopped on the tube, or chased around a soap shop, is all very new. “I’m still trying to get my head around it. There was a particularly tricky time recently when I had just lost a friend. Obviously bereavement is tough but life goes on, you’re out and about in your normal day, and your brain isn’t in the best place. And people still want that selfie and they don’t know. You can’t put that on them. It gets tricky trying to handle your personal and your public life.”

He prefers not to talk about his personal life, but he’s happy to discuss a recent trip to Rwanda, his first there in 12 years. His parents had nine siblings each, so there was a lot of family to see. “I’m not going to lie, I was a bit cautious about going back, because I was, like, ‘I wonder how they’re going to take me.’ I’ve entered the public sphere in a very specific way. But they’re so protective of me! Very, very protective and very proud.” He was in awe at the beauty he saw. “I didn’t feel like I was looking at real life. It’s just so nice to be able to fly that flag. That flag and my Scottish flag. I love that I come from both those places.”

Facebook Twitter Pinterest Stage player: with Nick Blakeley in The Claim. Photograph: Tristram Kenton/The Guardian

Sometimes, he says, people are confused by how he sounds. “I don’t think you expect to see a young black boy with skin fades coming out with a Scottish accent. Even me!” His accent tends to shift and adapt to wherever he is. “But way back when I first moved to London, there have been times when people have tried to fight me.”

On nights out, people would challenge him about where he’s from. “You get chatting, like, oh mate, where are you from? Oh I’m from Scotland. Lol, no, where are you actually from? Scotland. Why are you taking the piss? I’m not taking the piss. And people think you’re being a dick.” Confounding expectations, however, does have its benefits. “It’s booked me a lot of jobs. I’m not complaining.”

Gatwa has finished shooting season two of Sex Education, and is currently filming Last Letter from Your Lover, an adaptation of the Jojo Moyes novel, starring Felicity Jones (he plays her flatmate). Then he’s going to the US to shoot a film, where he will play the lead. “If I talk about it any more, I might get sued.” He’s happy, he says, taking roles where he can make people laugh and think at the same time. But ultimately, he has one goal from it all, and that’s to buy his mum a house. “Those are my dreams. Buy mum a house, build a school in Rwanda,” he says, grinning. “Then carry on making enough money to buy soaps from Lush.”

Sex Education series two is on Netflix from 17 January

Ncuti Gatwa styling by Bemi Shaw and grooming by Keshia West