Jessica Raine, Keeley Hawes and Robert Lindsay join the cast of Line of Duty

The return of the popular procedural series - which pulled in an average of 4.2 million viewers during its initial run - will begin with the dramatic ambush of a police convoy escorting a protected witness, resulting in the death of three officers and the serious injuries of their charge.

Lindsay will take on the role of Deputy Chief Constable Mike Dryden who takes personal control of the case, assigning anti-corruption unit AC-12 to investigate, while Hawes will play the incident's sole survivor, Detective Inspector Lindsay Denton.

Jessica Raine will portray newly-appointed DC Georgia Trotter who joins series one regulars DS Steve Arnott (Martin Compston), DC Kate Fleming (Vicky McClure) and Superintendent Ted Hastings (Adrian Dunbar) to investigate the case. But proceedings take an unexpected turn when key witness and survivor Denton becomes the subject of the unit's suspicions...

Speaking of her new role, Keeley Hawes said, "I'm thrilled to be joining the cast of Line of Duty and after reading Jed's incredible scripts I can't wait to take my character, DI Lindsay Denton, on the epic journey he has created for her.

"I loved the series so it's a real pleasure to be part of series two and working alongside such talented actors like Vicky McClure, Martin Compston and Robert Lindsay."

Controller of BBC2, Janice Hadlow, added, "Drama on BBC2 continues to enjoy an incredible resurgence and I'm delighted that Line of Duty, one of the channel's biggest hits last year, is returning, attracting a stellar cast to what promises to be another riveting thriller."

Written and executive produced by Jed Mercurio (Bodies, Cardiac Arrest), and directed by Douglas Mackinnon (Doctor Who) and Deniel Nettheim (The Hunter), Line of Duty will begin filming in Belfast later this month.