Played by Brian McCardle, Hunter was the leader of the Organised Crime Syndicate (OCG). He was a paedophile who groomed DI Matthew Cottan (Craig Parkinson) to be his man on the inside within AC-12. In the show, DI Steve Arnott (Martin Compston) states that the DNA match "runs of homozygosity". The definition of this is: “The state of possessing two identical forms of a particular gene, one inherited from each parent.” Kelly Macdonald as DS Joanne Davidson in ‘Line of Duty’ (BBC) While the episode didn’t actually state how Joanne is related to Tommy, a post it note on the wall at AC-12 reveals that she is the result of incest.