'Line of Duty' Series 3 has seen the regulars of AC-12 - Arnott, Fleming and their boss Hastings, not to mention that helpful colleague 'Dot' Cottan - joined by some faces new and old.
Each series has been critically acclaimed, with Lennie James' initial antagonist making way for Keeley Hawes, and then Daniel Mays. Jed Mercurio's scripts have famously stretched the actors, with the interview scenes alone covering as many as 27 pages, and taking whole days to shoot.
Just as well it's a pedigree cast involved, but where have we seen them before?
'Line of Duty' continues on BBC Two on Thursday at 9pm.