BBC News goes behind the scenes

Netflix/Heartstopper Season 3 A camera operator wearing a cap with his back to the photographer films Kit Connor and Joe Locke as they embrace and smile at each other. Kit's ginger hair is wet and he wears a grey hoodie, while Charlie has dark brown curls and wears a baggy green and white jumper. — Kit Connor and Joe Locke, who play boyfriends Nick and Charlie, joked it was hard getting used to kissing your friend on camera.

On a freezing cold November day in 2023, we’re driving up to a school on the outskirts of London. It appears disused and unremarkable – but then a sign reading ‘Truham High’ gives the game away.

This abandoned-looking building is actually the set of Netflix sensation Heartstopper, and on the day we visit, shooting for series three is well under way. The new episodes will be released on 3 October.

Inside, the hustle and bustle you might expect in a school corridor has been replaced with the organised chaos of a film set. The plain school interior is covered with colourful murals painted in the style of Alice Oseman’s graphic novels, which inspired the show.

Mr Ajayai’s art classroom is instantly recognisable.

In the first two series it’s been a safe space for Joe Locke’s character, Charlie, to go to when he’s having a hard time. During our visit he’s joined by Kit Connor, who plays Nick – and the conversation they’re filming looks difficult.

They’re sitting in a corner and speaking in hushed tones.

Heartstopper is known for its colourful scenery, like Mr Ajayai’s classroom, but the walls and corridors are painted over in between seasons so that other TV productions can use them

Josh Parry / BBC The corner of an art classroom used for filming Heartstopper. The counter tops and sinks are covered in bottles of paint and there is a mural of a tree with autumn leaves painted on the wall and along the window, its roots painted on to the floor — Heartstopper is known for its colourful scenery, like Mr Ajayai’s classroom, but the walls and corridors are painted over in between seasons so that other TV productions can use them

While the producers are tight-lipped about the detail of what they’re shooting, they do tell us “it’s quite an intense scene”.

They’re protective over how many people are in the room with the actors during more emotional scenes. Dozens of silent crew members are crammed into a room next door, watching intently on monitors while the actors do several takes.

The third series of the show deals with more serious topics than the first two; Charlie’s eating disorder will be a key storyline, and some characters will be having sex for the first time.

“We’ve always said the show grows up with the characters, which is definitely the case this year,” Locke says, speaking to us in a quick break before his next scene.

“The show deals with some more heavy topics like mental health, and growing up, so there’s a lot of ‘teenageness’.”

A major storyline for series three will focus on Charlie, played by Joe Locke, as he struggles with an eating disorder

The show has been praised for showcasing “queer joy” – shining a light on the positive elements of growing up as part of the LGBTQ+ community – but Locke says it feels important to make sure it is still realistic.

“It’s all about authenticity, and trying to make your portrayal of a topic that is quite intense and quite close to people’s hearts as true as possible,” he says.

During our visit it’s clear the cast members’ chemistry goes beyond their time on-screen. Throughout our interviews they have in-jokes and gently make fun of each other, which Connor says helps with the more difficult days on set.

“After filming we all just sort of pile into someone’s flat and spend time together, we have a great way of doing it where we don’t talk about work or anything like that,” he says.

“We all just go home, make dinner and criticise each other’s cooking skills.

“[Joe Locke] actually cooked a good chilli this time… last time it was a very, very bad chilli. This time Will, who plays Tao, had seconds… but he will eat anything.”

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While the friendships might be real, some of the most iconic locations in the show are actually flat-packed and assembled inside the school, as and when required.

During our visit, Nick’s bedroom is assembled in what would have been the school’s sports hall.

There are no lights as no scenes are planned here today, so we explore using our phone torches instead. Even in the semi-darkness, the attention to detail is clear.

From books about bisexuality, to Polaroid pictures of Nick and Charlie together, they’ve gone to painstaking lengths to make the bedroom a true reflection of the character’s journey throughout the series.

“The fans really notice everything, and have theories about even the tiniest of details… you should see some of the TikToks they make,” a member of the crew tells us.

It might not look like it from the outside, but this wooden box is actually Nick’s bedroom in the show. Each set is built as and when needed in the school’s sports hall

Josh Parry / BBC An exterior of a film set, propped up by scaffolding. It's a wooden box with windows and outside the windows are fake trees and shrubs. The floor is covered in cables and filming equipment. — It might not look like it from the outside, but this wooden box is actually Nick’s bedroom in the show. Each set is built as and when needed in the school’s sports hall

Just down the corridor from Nick’s flat-pack bedroom is the costume department, where designer Adam Dee says he likes giving mega-fans things to spot.

“If they’ve got a scene with an open wardrobe, [we’ll] sneak in some iconic pieces from previous series so the audience can spot them,” he says.

“With Elle, she has a sewing station in her room, so we managed to add in some bits and pieces to her wardrobe that are made from two other items we’ve sewed together, or vintage scarves we’ve turned into tops.”

Heartstopper was somewhat of a surprise hit for Netflix, and series one launched with very little promotion.

It became one of the top 10 most-watched English-language series within two days of its release and received an almost-unheard-of 100% rating on Rotten Tomatoes – something many critics have put down to the diverse on-screen representation.

Season three involves some of the show’s older characters turning 16 and starting to have sex.

Season three will show the developing relationship between Elle and Tao (Yasmin Finney and William Gao)

Netflix/Heartstopper Season 3 A scene from Hearstopper with Elle and Tao hugging on Tao's bed. Elle is resting her head on Tao's chest and they're staring at something off-camera. Both of them are wearing pyjamas and are lying on top of the covers. — Season three will show the developing relationship between Elle and Tao (Yasmin Finney and William Gao)

Yasmin Finney’s character, Elle, who is transgender, will be shown starting a sexual relationship with her on-screen boyfriend Tao (William Gao).

The sex lives of transgender characters are often left out of TV storylines.

Finney tells us: “It’s nice to have that representation of a trans person being able to have those sorts of relationships.

“It’s very sweet and I’m very blessed to be able to deliver that performance with Will.”

In the second series, Tobie Donovan’s character Isaac tells the rest of the characters he is asexual, meaning he experiences little or no sexual attraction. It’s another topic few TV shows have featured.

BBC News was given exclusive access behind the scenes to interview the cast; including Tobie Donovan (left) and William Gao (right)

Josh Parry / BBC A camera operator carrying equipment on her back points the camera at Tobie Donovan and William Gao, while a reporter holds out a microphone to interview them. The pair are both laughing. — BBC News was given exclusive access behind the scenes to interview the cast; including Tobie Donovan (left) and William Gao (right)

Donovan tells us he felt he wanted to do “lots of research” to make sure “he was doing justice to this community”.

He added: “There’s been sort of nothing like this on TV before, so I really wanted to make sure I got it right.

“I feel like, from our season two response, people were quite happy that even just to have anyone on screen that’s like a little bit of their story. It’s great for all of us.”