For many of the young cast of new Channel 4 drama The Gathering, it was their first time in professional acting roles – not that viewers are likely to be able to tell.

The secret to eliciting such quality performances from newcomers is to leave them to get on with it, lead director Gareth Bryn told the Liverpool premiere audience.

“Sometimes, the worst thing a director can do is direct,” he said. “You can talk it to death, so sometimes the best thing is not to say very much. Cast it well and create an environment of trust so they feel they can be brave and try stuff out, then just let them be themselves and do what they instinctively want to do. Let them use their talent.”

Last month’s premiere and Q&A was held on the home turf of the stylish Merseyside-set mystery. The debut TV script by novelist Helen Walsh follows a group of elite teenage gymnasts and free­runners with tangled love lives and toxic parents in the lead up to tragedy.

Walsh told the event: “One of the themes is control and how much freedom we should give our teens. Do we give them too much or not enough, and do we judge other parents? Are our kids safer in the online or offline world? In the first episode, Kelly is offline, jumping off the roof of a tower block, while Jessica is glued to her iPhone in her bedroom but navigating very adult worlds. Which is more dangerous?”

Walsh added that she was particularly concerned about the drama’s portrayal of immigrants: “I cared most about the character of Bazi, who’s a refugee” – and does parkour [traversing obstacles while running]. “We worked with an incredible charitable organisation, Imix, which tries to change the conversation about immigration. And I was so happy that we captured the camaraderie and community of free-running, which can get a bad press. It attracts a lot of kids who don’t fit into team sports at school and are neurodiverse. It’s a vital space for kids.”

The adult cast includes Warren Brown, Vinette Robinson and Richard Coyle, but it’s the newcomers who stand out. Eva Morgan said of her lead character: “I admire Kelly, she’s so bold, truthful and unapologetic. She was equally beautiful and heartbreaking to play. It feels cinematic and magical, the way it’s filmed, but then Liverpool is magical.”

The Gathering is made by World Productions, producer of Line of Duty and Vigil. Executive producer Simon Heath said: “We haven’t done any dramas with young characters for quite a while and I missed it. There’s a reward in finding new talent in front of and behind the camera. The Gathering looks so vibrant, and brilliant talent pops up even in the tiniest roles.

“I was excited to make a show that reflected my own experience of being a father to teenagers, and that captures the spirit of teens. ‘Are you drunk, Dad?’ I remember hearing just the other night.

“The themes of The Gathering are universal but the story is specific and local. There was never any question that we had to shoot it in Liverpool. It was wonderful to showcase the glory of the city.

“I have become a huge advocate for Liverpool. I don’t want to film in London because it’s a nightmare, I’d much rather film further north. You get much better value, which can be seen on screen. I really hope we can do a second series here.”

The Channel 4 event, was held with the support of RTS North West at the Everyman Liverpool on 13 May. The producer was Katie Paterson.