In the Footsteps of a Killer - S6-E7
Continuity mistake: During the interview at the bar, the quantity of coconut and rum in Tony Garret's glass changes between shots multiple times. Easiest bit to spot it is towards the end when he brags that he could find a dozen witnesses in an hour; as he says that line, the liquor barely covers half of the ice cubes, but after a brief cut on Ardal O'Hanlon, the glass is full enough to cover most of them. (00:26:00)