Few series by the streamers have made as much noise as Netflix’s Sex Education, which brings the genre of the US high-school teen drama to the UK – and adds plenty of gauche sex.

The global giant released the second season of the comedy-drama in January. A few days earlier, the first episode was premiered at a joint RTS Cymru Wales/Bafta Cymru event in Cardiff.

Jaws dropped around the cinema during what we can safely say – even this early in the year – will be 2020’s most astonishing opening sequence. Otis Milburn (Asa Butterfield) is shown trying and failing to control his newly discovered sexual urges in a scene that ends in excruciating embarrassment in front of his therapist mother, Jean (Gillian Anderson).

Season one of Sex Education was a huge critical success and, almost certainly, a commercial hit for Netflix. The US streamer is famously reticent about releasing viewing figures.

“We didn’t have any idea that people would respond to the show in this way and, particularly, that the breadth of audience would be as it is,” said executive producer Jamie Campbell, creative director of Eleven Film, which makes the series.

Campbell was speaking as part of a three-person panel with casting director Lauren Evans and location manager Midge Ferguson, which followed the screening of the first episode of the new eight-part series.

Sex Education attracts “an audience that is very youthful and an audience that is very senile – and lots [of people] in between,” joked Campbell. “People think it has something very contemporary to say, which can appeal both to very young and old people.”

The series, in which Otis Milburn offers advice on sex to his fellow sixth-form pupils – mixes hilarious teenage sexual confusion with a sensitive discussion of sex and relationships. But, added Campbell, Sex Education is not “didactic”; rather, it is “truthful and emotionally open, which people like”.

Campbell praised series creator Laurie Nunn. “The conceit of the show is very unusual and shouldn’t work,” he said. “It allows you to be broad comedically but also go to some quite dark and emotionally deep places.”

Director Ben Taylor’s input was as important, argued Campbell, as Nunn’s. He explained that Taylor, whose credits include Channel 4 comedy Catastrophe, married “Laurie’s vision” to the look and feel of the “American teen movies and high-school TV shows that we grew up with, particularly the John Hughes movies”. Hughes made his name with 1980s teen films such as The Breakfast Club and Pretty in Pink.

"An integrity co-ordinator was brought on board for filming “so that all these scenes of a sexual nature [could be] broken down and almost choreographed"

“There’s an innocence about those shows and an aspirational quality,” said Campbell. British series, he continued, tend to focus on “what a horrible experience [school] is”. “And often it is, so that’s fair enough, but one of the things we wanted to do was to say that our characters were going to look back and feel it was the best time of their lives, rather than a time to escape from.”

Sex Education’s cast is a mix of the famous and experienced – Anderson, Butterfield and, new for season two, Anne-Marie Duff – and first-timers.

Discussing how she cast the show, Lauren Evans admitted that, initially, “it was a daunting challenge”. “With a younger cast… some of whom had never [acted] before, it’s about feel… and trying to assess quickly whether they’ve got potential.”

Cast diversity, she said, was critical: “It was hugely important to find an eclectic ensemble that was representative, so everyone could see themselves on screen.”

The sexually explicit nature of the show led to Evans enduring “some of the most embarrassing phone calls of my life. These were young actors and I had to have a conversation [with them], making it transparent from the beginning that it’s got sexual content… and, especially in this climate, to make sure everybody feels that they’re armed with the knowledge of what the show’s about, how we’re going to shoot it and what is required of each character, so that they could make an informed decision before they committed [to it].”

An integrity co-ordinator was brought on board for filming “so that all these scenes of a sexual nature [could be] broken down and almost choreographed. Everyone talks through what they are and are not comfortable with – everyone has a voice,” said Evans.

“It is amazing to think that, even as recently as five years ago, I would say more than 90% of productions would have no parameters to work with,” added Campbell. “In physically intimate scenes… you’d just cross your fingers, go for it and hope that everyone was OK. That was good because people, on the whole, have good intentions, but you want to make sure that people feel and are safe.”

"Netflix told us... to make it the most "authorially" pure show that we could make"

Sex Education is set in the fictional Moordale Secondary, filmed in Caerleon, South Wales. The series makes the most of the Wye Valley’s many beauty spots, few of which have been seen in TV drama before.

Wales offered “extraordinary places to shoot”, said Campbell, and the opportunity to tap into South Wales’s ready supply of production crews. Since the BBC decided to shoot Doctor Who in Wales some 15 years ago, many shows, such as Casualty, have followed in its wake, bringing behind-the-camera talent with them.

“I found most of the locations driving around and getting lost,” explained location manager Midge Ferguson, who grew up in nearby Monmouth.

“A lot of shows end up using the same old locations – if you’ve ever been down Bute Street in [Cardiff] Bay, you know it’s had the shit shot out of it. Trying to find [places] that are fresh as well as aesthetically brilliant is what I’m after. Wales is just full of fantastic places.

“I had a good chat with the director, Ben Taylor, and the [production] designer, [Samantha Harley], about their thinking, so I had an idea of what I was looking for. Then, I literally headed off in a direction that I thought I might find them. I had good days and bad days.

“You spend a long time driving around and [asking yourself whether a location] is interesting or says something about a character. After a while, you get to know what works and why it works.”

“Midge took us around in his car and showed us [some locations outside] Caerleon,” recalled Campbell. “He was showing us stuff that we were getting blown away by.”

The show’s location, however, remains unspecified, which gives Sex Education a universal feel. “It is its own place,” said Campbell.

Working for Netflix, Campbell continued, had been “unequivocally a great experience”.

He added: “It really backed the script and Ben’s creative vision for how to shoot it, and told us to get on with it and make it the most ‘authorially’ pure show that we could make.

“That is an unusual approach. Most broadcasters ask you to shape it for a particular demographic.

“As producers of the show, it’s a very liberating process.”

Report by Matthew Bell. ‘Sex Education series two screening and Q&A’ was the first joint venture between RTS Cymru Wales and Bafta Cymru. It was held at the Chapter Arts Centre in Cardiff on 15 January and chaired by BBC Radio 1 presenter Steffan Powell. The event was produced by Edward Russell for RTS Cymru Wales.