Series six of the police procedural will rejoin AC-12 a year and a half on from the closure of Operation Pear Tree, following the Unit in their investigation of Detective Chief Inspector Joanne Davidson (Kelly Macdonald), who is working on an unsolved murder case.

“DCI Joanne Davidson will prove the most enigmatic adversary AC-12 have ever faced,” said writer and showrunner Jed Mercurio.

Superintendent Ted Hastings (Adrian Dunbar) will return to head the Unit having been exonerated in the series five finale, alongside fellow series leads DI Kate Fleming (Vicky McClure), DS Steve Arnott (Martin Compston) and DCS Patricia Carmichael (Anna Maxwell Martin).

Several first look images from set accompanied the announcement, which show behind the scenes shots of Martin Compston and Adrian Dunbar back to work.

Joining them are multiple newcomers including Shalom Brune-Franklin (Our Girl), Perry Fitzpatrick (This Is England), Andi Osho (Kiri) and Prasanna Puwanarajah (Doctor Foster).

As well as the new case, fans are looking forward to the reveal of the fourth Caddy in the corrupt organisation, H.

The new series will air on BBC One later this year. All previous series are available on BBC iPlayer.