Line of Duty creator Mercurio lifts lid on what viewers can expect in the future
The man who created Line of Duty has revealed the secrets behind television's most talked-about series.
Jed Mercurio described what inspires the complex plot of the hit BBC drama, which centres on a police anti-corruption unit.
The series, filmed in Belfast, has had more than eight million viewers on the edge of their seats.
Mercurio, the series creator, said: "I come up with the story ideas on my own.
"I like to sit at my desk... sometimes I get inspiration when I'm going about my normal day-to-day life. Then when I've come up with some sort of story, I get the editorial team on board and we try to develop it.
"I then write an outline of the first episode which takes about a week. It's only when we are all happy with the first episode do we start on the second."
The fourth series, starring Thandie Newton as DCI Roz Huntley, has been a huge hit with viewers.
The audience has grown steadily since the show moved to BBC1 this year, with 8.5 million viewers.
The previous three series aired on BBC2, where audiences peaked at 5.6 million.
In last night's dramatic finale, viewers saw DCI Huntley charged over the killing of forensics expert Tim Ifield in episode one - and the identity of the mysterious Balaclava man was finally revealed.
A fifth series of the show, which casts a new star for each season, has already been commissioned.
Mercurio added: "We definitely have a fifth, not a sixth... but we haven't started working on it yet. I need to think what the character is first.
He also revealed what viewers might expect in the next series.
"I want to look at the personal lives of all the regulars in series five - they've taken a backseat in this series to Roz Huntley, so it would be good to explore that side of things a bit more," he told the BBC.
"The regulars are definitely up for doing more."