The police thriller starring Lennie James, Martin Compston and Vicky McLure will shortly return to BBC Two, it has been confirmed.
Janice Hadlow, controller of the channel, said: "I'm so pleased to have this brilliantly realised thriller on BBC Two; it is a wonderful addition to the channel's rich landscape of drama.
"With fantastic writing from Jed Mercurio, great characterisation, tightly plotted detail and riveting performances from a stand out cast, I'm thrilled that this complex, contemporary drama has captured the imagination of such a loyal and appreciative audience."
Ben Stephenson, BBC Drama controller, added: "Jed Mercurio and World Productions have realised a brilliant series for BBC Two with Line of Duty that encapsulates my vision for bold, authored and utterly original drama on the channel."
The first series of Line of Duty concluded on BBC Two last night (July 24).
