Just a week after Line Of Duty creator Jed Mercurio teased fans with the news that his three stars were meeting the series six "secret guest stars", one of the newcomers has been revealed.
Trainspotting star Kelly Macdonald is joining the show as a "guest lead".
She will play Detective Chief Inspector Joanne Davidson, the senior investigating officer of an unsolved murder.
Announcing the news, the BBC said her "unconventional conduct raises suspicions at AC-12".
🚨 Kelly Macdonald will star as guest lead in the next series of #LineOfDuty. 🚨 She's playing Detective Chief Inspector Joanne Davidson, the senior investigating officer of an unsolved murder, whose unconventional conduct raises suspicions at AC-12. pic.twitter.com/nG99KaCppl
— BBC One (@BBCOne) November 19, 2019
Show creator Jed revealed he was "thrilled" Kelly was joining the show and said she would be playing AC-12’s "most enigmatic adversary yet".
The actress will join lead actors Martin Compston, Vicky McClure and Adrian Dunbar in the show's sixth series.
Another magnificent addition to the Line Of Duty team. Said it before, huge part of the show’s success is the phenomenal guest actors we’ve had.
Sarah was recently seen on screen in The Victim, while she's currently playing a police officer in BBC Two's Giri/Haji.
In Trainspotting, she played Ewan McGregor's schoolgirl love interest Diane. She reprised her role in 2017's T2 Trainspotting.
Piers Wenger, controller of BBC Drama, said: "We're excited for viewers to see what Jed's scripts have in store for her when she joins the Line Of Duty team."
The shows stars were also keen to welcome Kelly to the team.
Martin, who plays Steve Arnott, tweeted to say she would be "another magnificent addition" to the Line Of Duty team.
Another magnificent addition to the Line of Duty team. Said it before huge part of the show’s success is the phenomenal guest actors we’ve had. Kelly Macdonald will be up there with the best of them, what a talent what a career 🙌 Buzzing to get the tape started 😎 #lineofduty6 https://t.co/QAh6xyxwc0
— martin compston (@martin_compston) November 19, 2019
Vicky, who plays Kate Fleming, called her new co-star "phenomenal".
— Vicky McClure (@Vicky_McClure) November 19, 2019
Fans of the show are thrilled too.
Filming for the new series is due to start in the new year.
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