The scene in which Jimmy and Nick meet for coffee is filmed in a real coffee shop on the corner of William Street and Royal Avenue in Belfast across the street from the Belfast Central Library, the fictional setting for the Police Headquarters in the show.
Lee Ingleby (Nick Huntley) & Jason Watkins (Tim Ifield) also worked together on Watership Down (2018) as the voices of Captain Campion & Captain Orchis respectively.
Simon Millar has played four different characters over the course of the series:
- Episode 4.5 Lying Nest (2017) - DC Daniel Brightway (uncredited)
- Episode 4.4 Moral Superiority (2017) - DC Daniel Brightway (uncredited)
- Episode 4.3 In the Trap (2017) - DC Daniel Brightway
- Episode 4.2 Who Sows the Wind (2017) - DC Daniel Brightway
- Episode 4.1 In the Shadow of the Truth (2017) - DC Daniel Brightway (uncredited)
- Episode 3.3 Snake Pit (2016) - Cameraman (uncredited)
- Episode 2.2 Carly (2014) - Passer By (uncredited)
- Episode 2.1 The Ambush (2014) - Mourner (uncredited)