When DS Jones returns home after being dismissed by Taff, a modern door/window sensor can be seen on the inside of the front door behind him.
At least one of the vehicles in the funeral cortège had a licence plate with a blue EU GB strip, which were not in existence in the mid 1980s when the show was set.
At about 8 minutes in episode 4, when DS Stan Jones (Mark Addy) and CS Harris (Sean Gilder) are discussing Jones's version of the case, both of them refer to DSI Thomas Taff (Stephen Graham) as "DSI Jones". This is obviously an error.