How accurate and realistic is ITV's Dark Heart? Meet Chris Lang's police advisor | Radio Times

"You have to understand that there's dramatic licence that the TV company has to have as part of that development process," he tells RadioTimes.com. "You have to bend the rules ever so slightly."

Richards is a serving officer who has spent three decades in the police force, but prefers to keep his identity confidential to avoid attracting attention from people he's "dealt with" in the past.

His sideline as a police advisor began when he was asked to have a look at a script for Jed Mercurio's Line of Duty. These days, Richards is much in demand.

"He understands what I need," Lang told us, explaining the partnership they first forged on cold case crime drama Unforgotten. "He really understands the exigencies of making drama. We're not doing a documentary. You've got to find the line between pedantry and accuracy, because sometimes you can sacrifice a little realism for a dramatic moment – and he knows that line."

Dark Heart

One example: nitpickers might point out that real-life police interviews start with three or four minutes of procedural preamble. But that's not good TV.

"People say, that's not how you start an interview," Richards says, listing the irritating complaints that come back to him. "And I say, well, okay in reality it's not – but for a drama it is." These details might annoy police insiders, but "99.9% of the population that are watching it really don't care whether or not you go through that process."

He might give the writer space for "artistic licence", but there are some things it's vital to get right. From the very beginning he's on hand to help Lang structure his police team and set out the basics of the investigation.

"Chris leaves it quite broad when it initially comes through, because he knows that it's almost like having a blank page, and I do the colouring in," he explains. "How they attend that crime scene and who that's managed by, what resources turn up, who would do what, where the scene tape would be, and all those kind of things."

Dark Heart body

He adds: "Viewers get the feel for it being realistic from the very beginning because the team and the response to the investigation, the response to the crime, the way that the scene management is set up, the way that the investigative protocol and the interviews carry on – it just gives it that realistic flair."

So do the screenwriter and the policeman ever clash on the question of accuracy?

"Anything that wouldn't happen, I'm happy to say to Chris you're way off the mark here, and normally Chris would listen to me," Richards tells us. "But we've never reached that point where I've said, you're completely off the scale here, Chris, this needs to be reined in."

"I've always tried to accommodate his notes," Lang reports. "I don't think we've ever had a serious disagreement. No. Never. I don't think we've ever had a bit where I couldn't make it work for him and for me. So we've got a good understanding – he understands what I need, and vice versa."

Tom Brooke plays DS Rick Johnson in Dark Heart

In episode two of Dark Heart, Wagstaffe's police colleague DS Rick Thompson – played by Bodyguard's Tom Brooks – was revealed [SPOILER ALERT] as the killer behind the grisly murders of several paedophiles and suspected child molesters. Keeping his terminal cancer diagnosis a secret, he set out on a rampage of revenge which involved castrating one man and stuffing the testicles into his eye sockets.

Is this storyline totally unrealistic – or could it really happen?

Richards points out: "Thankfully they are few and far between, but there are police officers who were active who have been involved with criminal gangs, with criminal enterprise, they've been involved in serious violence, in those kind of serious incidents that have drawn extensive prison time."

He adds: "It's not about all police officers going rogue and all police officers being corrupt, that's not what we're saying, but what we're saying is I think it would be naive of anybody to think that police officers throughout the country haven't – and won't in the future – become involved in serious crime."

Dark Heart in London

Then there's the character of DI Wagstaffe himself. He's haunted by the murder of both his parents when he was only a teenager, a case which remains unsolved – and a traumatic event that has left him unable to form proper relationships.

"Will being a fundamentally flawed individual in his private life isn't completely unrealistic," Richards says.

"I've worked with people in the past that have had those issues going on in their private life, people that have got really significant domestic related breakdowns or breakdowns of relationships, estranged children...

"I look at Will and just think: not to the level that he's at, but we've all been through difficult times in our life."

Dark Heart continues on Wednesdays and Thursdays at 9pm on ITV

Eleanor Bley GriffithsDrama Editor, RadioTimes.com