Line of Duty For use in UK, Ireland or Benelux countries only Undated BBC handout photo of Vicky McClure as DI Kate Fleming and Martn Compston as DI Steve Arnott in Line of Duty. Series six of the BBC1 drama is set to come to a dramatic conclusion on Sunday evening. WARNING: This article contains spoilers about Line of Duty Season 6. OUR readers aren’t shy about voicing their opinions - especially when it comes to the final episode of hit BBC cop drama, Line of Duty. According to figures released by the Beeb yesterday, 12.8 million viewers were on the edge of their seat as the identity of criminal mastermind “H” - a corrupt top cop - was revealed.