The first details about the next series of Line Of Duty have been revealed with the confirmation of the latest adversary to be investigated by AC-12. 

Kelly Macdonald will play Detective Chief Inspector Joanne Davidson in the upcoming sixth season of the hit BBC drama, whose suspicious conduct will be investigated by the police anti-corruption unit. 

Kelly is best known for her roles in Trainspotting, Gosford Park, Boardwalk Empire and, most recently, The Victim and Giri/Haji.

She will officially join the cast when filming on the new series begins in 2020.

Her character, DCI Davidson, is the senior investigating officer of an unsolved murder, who Line of Duty writer and showrunner Jed Mercurio described as “the most enigmatic adversary AC-12 have ever faced”.

Returning to the show will be series leads Martin Compston, Vicky McClure and Adrian Dunbar, who play DS Steve Arnott, DI Kate Flemming and Superintendent Ted Hastings, respectively.

Kelly follows in the footsteps of previous AC-12 adversaries DCI Tony Gates (Lennie James), DI Lindsay Denton (Keeley Hawes), Sergeant Danny Waldron (Daniel Mays), DCI Roz Huntley and DS John Corbett (Stephen Graham). 

The fifth series of Line Of Duty concluded earlier this year and revealed legal counsel Gill Biggeloe had been setting up AC-12 boss Ted Hastings as mysterious organised crime boss “H”.

It was later confirmed from a closer examination of DI Matthew Cottan’s dying declaration that “H” was actually a clue rather than a person, indicating there are four high ranking officers in league with organised crime.

So far, Cottan, ACC Derek Hilton, Biggeloe have already been unmasked, with another still at large, which is likely to explored in the sixth series. 

The BBC has said it will announce further details about the new series “in due course”.