We don’t know very much about the fifth series, except that star Martin Compston teased that the script is “immense” and Mercurio said the new episodes feel like “very fresh territory”.
He revealed: “There are things we haven’t done before, characters we haven’t seen before and that I think’s part of the construction of the series.”
Who will star in series five?
Adrian Dunbar, Vicky McClure and Martin Compston are expected to reprise their roles as the officers of AC-12.
Line of Duty usually has a guest star as the focus of each investigation – previous series have seen Keeley Hawes and Thandie Newton among those to come under scrutiny – but season five’s casting is yet to be announced.
Sign up to the Radio Times newsletter for the latest TV and entertainment news