Line of Duty: Key moments from Series 6 Episode 3 Things are really heating up in AC-12's investigation into the handling of Operation Lighthouse Steve Arnott (played by Martin Compston) in Line of Duty season 6 (Image: Steffan Hill) Never miss a thing from Belfast and beyond - sign up for FREE newsletter direct to your inboxInvalid EmailSomething went wrong, please try again later. Subscribe When you subscribe we will use the information you provide to send you these newsletters. Sometimes they’ll include recommendations for other related newsletters or services we offer. OurPrivacy Noticeexplains more about how we use your data, and your rights. You can unsubscribe at any time.