Line of Duty Guest cast, played by George Costigan Episode 3x04: Episode 4 (Apr 14, 2016) Episode 3x05: Episode 5 (Apr 21, 2016) Episode 6x02: Episode 2 (Mar 28, 2021) Episode 6x05: Episode 5 (Apr 18, 2021) Episode 6x07: Episode 7 (May 2, 2021)