HOW does it feel to become famous overnight? Ncuti Gatwa is a good man to ask. Last year, the Rwandan-Scottish actor stepped on to a plane in New York in relative obscurity (“I had 700 followers on Instagram”) and by the time his flight landed in London eight hours later, that figure had leapt up by several hundred thousand.

While Gatwa, 27, was soaring somewhere high over the Atlantic, the debut series of Sex Education had begun streaming on Netflix. His character – the ebullient, flamboyant and adorable Eric Effiong – was an immediate hit with viewers.

Suddenly everyone wanted to know all about Gatwa. “It was pretty instant,” he reflects. “In the weeks following, being out on the street and getting recognised and stopped was the weirdest experience of my life.”

He breaks off into a belly laugh at the memory. “Buying my pain aux raisins and someone wanting a selfie was so confusing. Fame is something I still haven’t got my head around. It will be quite a long process of trying to get used to it.”

Nowhere, it seems, is safe from the adoring masses. “The strangest place I have been recognised is a urinal,” he says. “I was like: ‘Why are you talking to me now?’. That is the weirdest thing, but the most uncomfortable is when you are on the street and someone just grabs you.

“Obviously they recognise you, but you don’t know them. Being grabbed randomly out of nowhere is quite scary. I am from Fife, so if you grab me randomly out of nowhere, it might not end well for you,” he jokes. “That is something I have had to get used to. Most people are very nice.”

When Sex Education debuted last January, it generated a huge buzz – largely through word-of-mouth – and went on to become one of the most-streamed Netflix shows of the year, garnering more UK viewers than cult series such as The Umbrella Academy, You and Black Mirror.

It’s easy to see why. The comedy-drama deftly taps into the zeitgeist of what it means to be a Gen Z teenager or young adult today (kudos to the show’s creator Laurie Nunn, it bears all hallmarks of the way that the late John Hughes spoke to a Gen X audience in the 1980s with his coming-of-age epics Sixteen Candles and The Breakfast Club).

The cast is led by Asa Butterfield, known for his roles in The Boy in the Striped Pyjamas, Hugo and Miss Peregrine’s Home for Peculiar Children. He plays socially awkward teen Otis Milburn, with Gillian Anderson of The X-Files and The Fall fame as his overbearing, sex therapist mother.

Otis is befriended by classmate Maeve Wiley – a misfit bad-girl who, played by Emma Mackey, is whip-smart, savage and savvy – and together they set up an ad-hoc sex therapy clinic giving relationship advice to their clueless peers.

Otis’s best friend Eric (the delectable Gatwa) has his own gripping and powerful story arc, navigating life within the constraints of a strict, religious Ghanaian-Nigerian family, while exploring his identity as a gay, black teen.

Be it experiencing the perils of an overactive gag reflex (one memorable scene involves a banana) or an unexpected tryst with the resident school bully, the biggest joy is that Eric isn’t relegated to the tired old cliche of a gay and/or black best friend straight from Central Casting.

He is a force of nature in his own right, something which has struck a chord among many viewers. “I feel very honoured to play a character like Eric, who is gay, but his sexuality isn’t his defining feature or used as comic relief,” says Gatwa.

“It is just who he is – we are watching a young boy be who he is. That, I think, has had a bit of an impact in the gay community.

“I get lots of messages from people who live all over the world, from places where being gay might be illegal or they might be killed and if their family knew, things would be bad for them. I get messages every day from people like that telling me how much the show and Eric has helped them.

“It is important that we continue to keep telling stories from new perspectives and have proper representation on our screens, because it is educational and empowering.”

Gatwa admits that the popularity of Sex Education, which has returned for a second series this month, was something he was unprepared for. Nor did the actor envisage becoming its breakout star.

“No. Full stop. I didn’t think it was going to take off in the way it did,” he says. “The show release had a good hype and I was waiting for the hype to die down. And it didn’t.” He laughs incredulously. “It is fantastic being part of a show like this. It is something I am very, very proud of.”

With time to take stock and reflect, I’m curious to hear Gatwa’s take on why Sex Education has had such a far-reaching impact, amassing a loyal fanbase and the plaudits of TV critics alike.

“I think people are drawn to the fact that it tackles issues in a way where we aren’t trying to preach to anyone or shame anybody,” he asserts. “We are just trying to show the world for what it is.

“It is a show of its time as well. We are having a lot of conversations about diversity and inclusion. A couple of years ago we had the start of the #MeToo movement which was something that was very necessary.

“We are challenging the way we think and interact with each other in our society. The world is having a real rethink about how we communicate and interact with each other. I think Sex Ed is a show that epitomises this moment that is happening in the world right now.”

He pauses. “Does that make sense? Or have I just waffled?” Like much of what Gatwa says, his words provide illuminating insight. Thoughtful and articulate, he is not only an excellent spokesperson for the show, but one could argue, his generation.

Technically – having been born in 1992 – he’s a millennial rather than Gen Z, although Gatwa makes a convincing teenager. What’s it like to rewind the clock a decade? The question prompts another guffaw of laughter. “I’m not going to lie. It is a weird frame of mind you have to put yourself in.”

Stepping into the fictional Moordale Secondary School with its classrooms, echoing corridors and infamous toilet block – the show is shot at the former University of South Wales campus at Caerleon on the outskirts of Newport – definitely helps, he attests.

“There are lockers around us, I’ve got a backpack on and I’m riding a bike,” says Gatwa. “You would be surprised how quickly you revert to being a kid again. All of us, the actors and crew, we become like big kids on set.”

His own childhood was spent in Scotland. When he was two, Gatwa’s family left Rwanda as refugees, fleeing the genocide. He grew up in Oxgangs in the south-west of Edinburgh, and then, when he was 15, they moved to Dunfermline.

Arriving at a new secondary school, Gatwa found himself the target of bullies, who set up a racist social media page about him. It is a horrendous and incomprehensible scenario for any young person to experience, yet there is no lingering bitterness as he speaks.

“Edinburgh is a city, so it was a little bit more multicultural,” he recalls. “It was easier in Edinburgh. Although growing up in Oxgangs wasn’t always easy. Moving to Fife that is when it became a bit more of a problem.

“Obviously, it wasn’t nice. But it was one of those things I had always known, so I was almost desensitised to it. At the same time, my parents very much instilled a sense of pride within myself and about where I come from, so I was never too disheartened when I was going home.

“Also, I know that I’m pretty f***ing cool,” says Gatwa, laughing to lighten the mood. “I’m pretty aware of that. I thought: ‘You lot are going to like me eventually.’ When I moved to Dunfermline, it was the first time I realised how different I looked to everyone else who grew up around me.

“That is where I learned about ignorance and hate. I think, for them, they had probably never seen a black person in their life. The way they behaved was something that is never excusable, but I feel like it was coming from a place of ignorance.”

In the end, he did win them over, eventually becoming friends with his former “bullies” (the quote marks are insisted upon by Gatwa) and professes that he harbours no grudges.

“Scotland will always be my home. It is where I am from and it is where I grew up. I love the warmth of Scottish people. When I think back on that time, I don’t think horror and torment. It was a bit tricky but, ultimately, has made me a stronger person.”

It’s an admirable way to look at things. Not everyone would have his strength. When Gatwa describes himself as a “Rwandan-Scotsman”, the pride is palpable. “Rwanda is the country that birthed me and Scotland is the country that raised me. They are both dear places in my heart.”

When it came to a career, it is difficult to imagine he would have considered anything but acting. Yet, it took a little while, admits Gatwa, for the penny to drop that it could be a legitimate way to make a living.

“I was a bit, um, highly spirited in school,” he says, grasping for a diplomatic way to phrase his teenage jinks. “My parents are both very academic and initially wanted me to follow an academic route. I thought about doing that, but it was not for me.

“It got to the point where, really and truly, drama was the only subject I was turning up for. My teachers spotted that, and they saw how much I loved it. They said I should think about going to drama school, but I didn’t think that was even a possibility.

“I didn’t really know that drama school was a thing. I certainly didn’t think being a young, working-class, black Scottish person, that I could go on to be an actor and forge a successful career. The first time someone said it, I laughed.

“But then they kept saying it. They told me about RSAMD [now the Royal Conservatoire of Scotland] in Glasgow. I went along, auditioned and they sent me my unconditional offer really quickly. I thought: ‘This must be for me.’

“I love telling stories. I’m a bit of a chatterbox as you can tell. The fact I have made my job something where I can use words, that is so cool to me. I took to it like a duck to water. I thought: ‘This is amazing. I want to do this for the rest of my life.’”

Gatwa cut his teeth in theatre and after studying at the Royal Conservatoire went on to win a place on the graduate scheme at Dundee Rep where he performed in the acclaimed 2013 revival of David Greig’s Victoria.

He later landed roles at the Shakespeare’s Globe theatre in London in A Midsummer Night’s Dream and 946: The Amazing Story of Adolphus Tips.

His first TV appearance was in BBC Four sitcom Bob Servant. Gatwa played a customer queueing up at the bold Bob’s burger van in Broughty Ferry. “It was!” he enthuses, when I remind him. “Thank you! No one ever brings that up. I played: ‘Burger Man No. 2’.

“It was my first time in front of a camera and getting a mic put on. I had one line. But it was such a fun day. I learned so much about the etiquette of being on set.”

Gatwa also had a part as a police officer in Stonemouth, the BBC Scotland adaptation of the late Iain Banks’s novel, which aired in 2015. “It was great show and a great book,” he says. “That was another good learning opportunity for me being able to shoot in Scotland in a gripping drama.”

Then came Sex Education. And his public profile exploded into the stratosphere. When we talk, Gatwa is in a London hotel amid the whirlwind that is the gargantuan Netflix publicity machine.

The conveyor belt interview scenario is never a great way to make a connection with an interview subject, yet with Gatwa the conversation flows easily. While fiercely private about his life off camera, he does touch briefly on his family and being the youngest of three children.

“My dad works in churches – he has always worked in churches. He is now a professor of theology in Rwanda and a minister. My mum works for our incredible, amazing and wonderful NHS.”

What about childhood heroes? Who did Gatwa look up to or have posters of on his bedroom wall? “Well, I didn’t have posters of them on my wall because that would be weird, but my mum and dad were my heroes,” he says, a smile in his voice.

“When you are a child of immigrants, you see your parents struggle and everything they have to go through for you. My parents always made me feel very loved and never feel bad about anything, but I saw how hard they worked.

“My mum, moving here, building everything she has, raising us three kids with no money, when she didn’t know the language and culture. They were definitely my heroes growing up.”

For those who fell in love with his on-screen alter ego Eric, there’s plenty more to come in series two. “Eric is a little bit more comfortable within himself and settled,” says Gatwa. “Not in a particularly overt type of way, but he is more grounded. And unapologetic as well.

“He is continuing his journey of self-discovery, learning about what is important to him and how he wants to walk through this world. There are a few new characters that arrive into Moordale who are causing a stir. One of them catches his eye, so we will see what happens there.”

Sex Education series two is available to watch on Netflix now