Line of Duty's Jed Mercurio on creating "gigantic stakes" in his new graphic sci-fi novel Sleeper

"It was really about creating the gigantic stakes of the story," Mercurio tells RadioTimes.com. "But in order for the conspiracy thriller to work in a way that the present day readership would would recognise as being plausible, it felt like we had to borrow from the corporate world. And the idea that there would be very high value corporate interests in deep space, it felt like that was hugely important to creating a believable reality, or believable context around the story.

"Clearly, energy is something that is going to continue to be of huge importance to to human civilisation for the foreseeable future. You know, it's hard to imagine a human society that isn't dependent on energy. And so it just felt like a very straightforward proposal to invoke that."

On this dystopian vision of future climate wars, Puwanarajah adds: "I just think it's a question that's not going anywhere, anytime soon. And I think that underpins so many of our challenges globally, in terms of coastal flooding, resource management, the way that economies function, who's fighting wars with who... It sits above and beneath everything. And so it's the way, in the book, to talk about those things... I think it has a realistic take on human behaviour as it relates to governments and climates."

The novel, which is illustrated by Coke Navarro, sees DS-5 arrive at an International Space Station orbiting around Titan (Saturn's moon), where he is due to be "decommissioned" before he gets too old and starts glitching. But just before he is "terminated" (with a gun to the head), a mysterious and deadly explosion sends him crashing down to Titan – where he automatically deploys on a new and final mission to find out what happened. However, it's a race against time as his ageing technology begins to fail, and dark human memories resurface from the time before he was transformed into a Sleeper.

Though the setting and the sci-fi concept are a world away from Line of Duty (quite literally), there are plenty of echoes of Mercurio's most famous show between the pages of this novel. Because DS-5 wants one thing and one thing only, Ted Hastings-style: to complete his mission and uncover the truth, no matter how inconvenient. On the way, he comes across police officers and powerful figures who have other motives.

"There's something universal about law enforcement stories," Mercurio tells us. "Usually you have a crime, and most people would want to see justice done. So you immediately create a set of expectations and a set of stakes that the reader is invested in."

While law enforcement is definitely Mercurio's beat, the screenwriter – who is a former junior doctor – is also known for medical dramas such as Bodies, Cardiac Arrest and Critical. And given that Puwanarajah also worked as a hospital doctor for three and a half years, you might expect them to team up on something closer to home.

But Mercurio explains: "We wanted to do something that felt like it was a thriller, rather than medical fiction. There are elements of medical knowledge in the construction of Sleeper – the basis of the protagonist being biologically enhanced, for example, that was something that we discussed from a medical viewpoint. But ultimately, we wanted to sort of blend the western with the the science fiction conspiracy thriller."

On how the collaboration with Puwanarajah came about, he adds: "I knew that he'd been a doctor, before he got into the arts. And so we had kind of a similar background, and then we just started talking about collaboration... he was just a new writing voice that I was really excited to work with. And so we started talking about some ideas. And because we both come from a scientific background, when it came to discussing a science fiction idea, it was very productive."

This is Puwanarajah's first novel, but not Mercurio's. He's previously written Bodies (2002), which became a TV show, and Ascent (2007), which he abridged for a graphic novel a few years later.

"I'm a big fan of graphic novels," he tells us. "I think what I really like about them is that they are a combination of the very personal individual experience of reading a novel with the opportunity for the creators to focus the visual imagination down to their own aesthetics. The process of reading a novel is you take the description that's in the novel, but the imagination of the reader works to create a kind of visual model of the worlds that are being created by the author or authors.

"And so the graphic novel allows people who do that repeatedly through screenwriting and television production, to direct the imagination in a particular way. And so that's why Prasanna and I then collaborated with Coke, and we worked on the visualisation – because Prasanna's a director as well as a writer and actor. And so we're accustomed to visually shaping our work."

But, as Puwanarajah reveals, Sleeper actually began life as a potential TV series. He says: "We started writing scripts. Back and forth, back and forth. We did an outline or kind of show Bible type thing. And then we were talking to studios and channels in LA about doing the show. And we had two options, but we couldn't get a channel for it. So we just kind of thought, maybe there's a way of doing it here, and we spoke to some of the channels here. In general, the perception was that it was just too big to make.

"And Jed is a novelist, and one of his novels he's kind of repurposed as a graphic novel. And so he had the brilliant idea to just write it as a book, as a graphic novel series."

They then recruited Spanish illustrator Navarro, who tells us: "I did the poster for a play that Prasanna was directing at the Royal Shakespeare Company. So, after we finished the poster, he came to me saying he had to talk to me about this project." Navarro heard the story, and signed right up: "I've been fascinated by space since I was a kid."

Puwanarajah adds: "If, down the line, it were possible to restart conversations that we were having about it being a piece for television, yeah, we will absolutely be doing that." But for now, work on the second Sleeper graphic novel is already underway. If it's a hit, there could be many more.

So what about doing things the other way around, we ask? What about making a TV drama into a graphic novel? Like, say, Line of Duty...?

"I've never been asked that!" says Mercurio. But he doesn't wholly rule it out: "If somebody wanted to, then I imagine there would be a way that could happen. But personally, no, I think that the form that it exists in now, as a TV show, feels like the best form it could exist in."

Sleeper by Jed Mercurio, Prasanna Puwanarajah & Coke Navarro is published on Thursday 5th August (Scribner, £16.99).

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