The hidden world of witness protection is fertile ground for programme-makers. “When I started work on Protection, I began to see how clandestine witness protection is,” says Kris Mrksa, lead writer on a new ITV six-part drama.

“I hadn’t grasped how completely witnesses cut ties and start over. And police officers need to hide their own identities ­– if criminals knew who they were, they could follow them to safe houses. That aspect made it feel like espionage; they were spies rather than cops.”

We’ve seen witness protection as the central narrative in international TV hits like Lilyhammer and In Plain Sight and providing key storylines in Line of Duty and EastEnders. Now a UK drama series gives audiences an authentic view of this murky environment.

Protection stars Bafta-nominated Siobhan Finneran (Happy Valley, Alma’s Not Normal) as DI Liz Nyles, who is protecting an accountant and his family before he testifies against his ex-boss, a drug trafficker.

Their location is compromised and the family is found shot dead at the safe house. When Nyles hears that her secret lover (Barry Ward) was also murdered at the same location, a shadow is cast on his motivations and her future in the police. “Is there any chance you slipped up here?” her boss (Ace Bhatti) asks in the first episode. “I always follow protocol,” Nyles replies, losing her last chance to come clean.

The realities of witness protection were gleaned from Gary Madden, a police officer for more than 30 years, who approached New Pictures (Catherine the Great, The Missing, Indian Summers) about making a TV drama that gave a deeper insight into the process. Charlie Hampton, Executive Producer at the company, says: “We took the concept to Kris, and he was intrigued. He was drawn to the secrecy element and wanted to explore it in a le Carré-esque way, leaning into the moral compromise that witness protection officers accept. They must keep people safe, no matter who they are.”

The timing was perfect. Just as Madden approached New Pictures, Mrksa and the production company were wrapping on ITV’s White House Farm and were ready for another crime story. Madden’s concept, fleshed out by Mrksa, proved a natural fit.

Hampton says: “ITV has a strong history of crime dramas. Polly [Hill, Head of Drama] responds to stories that are authentic but also have emotional truth. That’s what came through when Kris developed the characters.”

Mrksa’s success in his native Australia with true-crime series Underbelly and novel adaptation The Slap encouraged him to try his luck in Britain. He says: “Crime drama is a genre the UK does very well. Even in the US, where the industry can be insular, there’s enormous respect for UK police shows and crime dramas.”

The character of DI Nyles was pivotal. “I was thinking about the ‘sandwich generation’, who have kids while also caring for ageing parents. That often falls to women, and I wondered how a witness protection officer would handle it. It made sense for her adversary to be a woman of a similar age, and without those domestic pressures.”

Stepping into that role is Katherine Kelly as DCI Hannah Wheatley, who is investigating the shooting at the safe house. This reunites the two Happy Valley actors, which was a coup for New Pictures, says Hampton. “Their chemistry on screen is great.”

Mrksa led a writing team of three; Polly Buckle and Giula Sandler helped develop story arcs and each wrote episodes. This approach has some of the benefits of the US-style writers room while not straying too far from the UK’s preference for a single writer’s voice. It’s Mrksa’s preferred way of working. “It’s something we’ve always done in Australia and is becoming more common in the UK,” he says. “I’ve only once worked in a full-scale US writers room and, while some see it as a luxury, I don’t miss it.

“A small room is more effective. It speeds up development and ensures the additional writers are involved in shaping the story. That gives them ownership and a deeper understanding of the show.”

The production was funded by ITV and All3Media’s international distribution arm. “Budgets are always a challenge,” says Hampton. “As always, we aimed to deliver more than what the budget strictly allowed for, which is just part of the job.”

Norwegian director Simen Alsvik (The Nest, Fenris) agrees: “We don’t have huge budgets in Scandinavia so we’re used to making the most of our resources,” he says.

Filming took place in summer 2023, in and around Liverpool, which offered several very different locations, all close to one another. “It’s small, so it’s easier to do unit moves there compared with London,” explains Alsvik. “Liverpool has a great visual quality, with the river, eclectic city centre, gorgeous bridges, and architecture that’s very British.”

To set a tense visual tone, Alsvik drew from series such as Mare of Easttown, Homeland and Sharp Objects. The family life of Nyles was key. “It was important to tease that out, but it’s also a bit of a spy show, and [we needed] to explain how the protection unit works, so it was a challenge to establish all that without being too expositional.”

Maintaining dramatic tension across the six episodes, as Nyles’s professional wranglings invade her home life, was essential. “The threat becomes more personal for Liz,” says Hampton. “Her family, as well as Amy [the surviving daughter of the accountant], find themselves in jeopardy. Liz questions which of her colleagues she can trust, especially as she tries to uncover what her lover was really up to.”

Protection has already been aired to acclaim in Scandinavia and to more mixed reviews in the US. “There’s been a lot of positive feedback,” says Alsvik. “People are seeing it as bingeworthy, especially with a female audience, because of Siobhan playing this strong female lead.”

Yet, says Hampton, “because this was an ITV commission, our focus was on what works for ITV. We wanted to embrace the Britishness. But, of course, it’s great when a show resonates internationally. You always hope that a show will travel.”

Protection is on ITVX and airing weekly on ITV1 from 16 March.