Tom Riley has said everyone involved in his new police drama Dark Heart had to work extra hard to make it stand out because the calibre of television is so strong nowadays.

The programme is returning for a full six-part series on ITV, after a pilot on ITV Encore in 2016.

Riley plays DI Will Wagstaffe, a man haunted by the murder of his parents, while Charlotte Riley plays his sister and Miranda Raison stars as his girlfriend.

He said: “There are a lot of procedural dramas already so you want to stand out.

“But not just for the show. We wanted to stand out for ourselves. We wanted to make something that excited us. That felt vital, fresh and new.

Charlotte Riley at a premiere
Charlotte Riley (Ian West/PA)

“We’ve all been fighting and working hard to make it very character-driven, very unexpected endings, not necessarily the most satisfying conclusion. It’s messier, like real life is.

“In the age of prestige TV, it’s also very important to make yourself look and feel as expensive, classy and different than the average run-of-the-mill dramas.”

Dark Heart was penned by acclaimed writer Chris Lang and was inspired by characters created by novelist Adam Creed, who has written a series of books featuring Will Wagstaffe.

Miranda Raison at a premiere
Miranda Raison (PA)

In the first instalment, Wagstaffe is at London City Airport when his colleague DC Josie Chancellor (Anjli Mohindra) calls him to tell him there has been a gruesome murder.

Wagstaffe is confronted by a horrific scene – Ray Collins (Mark Fleischmann), a man in his mid-thirties, has been tied to his own bed, choked and severely mutilated.

Riley said the series focuses on “justice and how we define it”.

“It’s also caught up inherently in the character of ‘Staffe’,” he said. “In that there are these shades of grey to morality.

“What is right and what is wrong and those that are seeking a particular form of justice – are they right or wrong?”