Line of Duty, the BBC2 police corruption drama starring Keeley Hawes that has kept more than 3 million viewers gripped each week, will be returning for a third series.
The thriller, based around an anti-corruption unit's internal investigations of fellow police officers, concludes its six-part run on Wednesday night when all should be revealed about the show's central mysteries – who staged the ambush that led to the death of three police officers and who killed 15-year-old Carly.
Line of Duty stars Hawes – in what critics regard as one of her finest performances – as DI Lindsay Denton, who is the only survivor of the ambush in the opening episode and a suspect; Adrian Dunbar, as anti-corruption boss Superintendent Ted Hastings and Martin Compston as DS Steve Arnott.
The show has steadily increased its ratings since it returned in February, climbing from a consolidated audience – including seven-day, catch-up viewing on Sky+ and other digital video recording devices – of2.7 million for its first episode to 3.5 million as it headed to its conclusion.
It is understood the BBC will confirm the third series commission once a new BBC2 controller is appointed. Janice Hadlow, who originally commissioned Line of Duty with drama controller Ben Stephenson, stepped down earlier this month.
Simon Heath, the show's executive producer, said talks were already under way about "potential fertile story areas for series three".
"[We've discussed] what that might be and what the character or characters [at the centre of it] might be, but there's plenty of mileage in police corruption," he told Broadcast magazine.
"[Line of Duty] was always designed as a long-running series – something that could come back for five series with each season having a different, hopefully, kind of investigation, as well as a different character under the spotlight."
Heath added that Line of Duty creator Jed Mercurio, whose credits include Cardiac Arrest and Bodies, will start writing the next series once he has finished work on Sky1 medical drama Critical.
Mercurio said he was "delighted and hugely flattered" by the reaction to Line of Duty and hoped to be able to reward fans' loyalty with a third series.
"What makes television so attractive to writers is that the medium allows your work to be seen by millions of people, but in recent years the viewing experience has become increasingly atomised," he added.
"To have people caught up by stories and characters that I've invented, to the extent that they've become part of everyday conversation, is incredibly fulfilling – and a tiny bit surreal."
The first series shown in 2012, featuring Lennie James, was BBC2's best-performing drama series in 10 years.
Stephenson said that he commissioned shows like Line of Duty and The Fall as he spotted there was a "gap in British television" for more complicated dramas in the same vein as the "complicated moodiness" in 1970s BBC shows like Tinker, Tailor, Soldier, Spy.
He said that "they don't take any prisoners in terms of depth of content, you can't really watch them without concentrating" and some audiences "love that". It is thought that BBC2 drama budget is between £20-£50m and Stephenson pointed out BBC2 now has three returning series, more than it ever has before. He said despite cuts to the licence fee for the next few years the "funding is sustained across the next few years" for BBC2 drama.
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