BBC News By Ella Wills image captionMartin Compston has played Steve Arnott since Line Of Duty began in 2012 Warning: This article contains spoilers for season six of Line of Duty, including Sunday's finale The reviews are in for the series finale of BBC drama Line of Duty - and opinions, it's fair to say, are mixed. Series six of the show, which first aired in 2012, ended on Sunday night. Created by British writer Jed Mercurio, Line of Duty stars Martin Compston as DI Steve Arnott, Vicky McClure as DI Kate Fleming and Kelly Macdonald as acting DS Joanne Davidson. It has been a ratings hit fo...