And now, for anyone who missed it - or wants to watch again - the first series of Line of Duty will be shown on BBC One starting tonight.
The series will air on Monday and Tuesday nights at 9pm.
Series one starred Lennie James as guest series lead DCI Tony Gates, alongside series leads Martin Compston (Steve Arnott), Adrian Dunbar (Ted Hastings) and Vicky McClure (Kate Fleming).
It also introduced viewers to Craig Parkinson as DS ‘Dot’ Cottan, Neil Morrissey as DC Nigel Morton, Paul Higgins as CS Derek Hilton, Nigel Boyle as DI Ian Buckells, Gregory Piper as Ryan Pilkington, and Gina McKee as Jackie Laverty - characters who would all return, in one way or another, for later series.
Line of Duty writer, Jed Mercurio said: "I’m delighted the BBC are giving new viewers and existing fans a chance to watch from the very beginning.”
An air date has yet to be set for the sixth series.