Trainspotting's Kelly MacDonald is joining Line of Duty season six as 'the most enigmatic adversary AC-12 have ever faced'.

The actress will play Detective Chief Inspector Joanne Davidson, the senior investigating officer of an unsolved murder whose unconventional conduct raises suspicions at AC-12. And while not much else has been revealed about her character, we're already intrigued - especially after Jed Mercurio's comments about her character. [caption id="attachment_489346" align="alignnone" width="1364"] Kelly Macdonald[/caption] "We're honoured that Kelly Macdonald will join Martin, Vicky and Adrian in series six of Line Of Duty," he said. "DCI Joanne Davidson will prove the most enigmatic adversary AC-12 have ever faced." She will start work on Line Of Duty series six when filming begins next year. And while there is no premiere date set just yet, Jed Mercurio revealed earlier this year that he was hoping AC-12 would be returning to our telly screens in 2020. “I would hope it’s sometime in 2020, next year. But that’s not something that we’re able to confirm," he told Radio Times earlier this year. And he recently teased the arrival of some "secret guest stars" for the season ahead, as he shared a reunion photo with Vicky McClure, Martin Compston and 'the Gaffer' Adrian Dunbar. Needless to say, he sent fans into an absolute frenzy with the photo - as many of them are looking for answers after that big reveal at the end of season five. Line of Duty season five came to an end back in March 2019, with a twist that proved to be very divisive amongst fans.