Revealing mistake: Dwayne supposedly swapped the rum with Humphrey, but if you pay attention during the time when JP hands them the glasses, it simply does not happen. (00:26:00)
Revealing mistake: Florence and Humphrey are reading the article about the young Dexter Allen from the Hackney Gazette. Behind the article, Florence has her mail open. Amazingly enough, the names of the people she received mail from (Joshua, David, Faye, a Customer service) are the same ones as the victims in She Was Murdered Twice, season 4 episode 7 when one of the suspects opened it from a public computer. (00:30:45)
Revealing mistake: While they are checking out Matt Holt's discount Facebook page (Face-spaces dot com) on the computer, behind the browser window there's an open file with a fingerprint, and like in another episode of this series, it's a fingerprint not related at all to this case, but one from three years earlier, the episode of season 3 "Ye of Little Faith", this time from the victim of that case Natasha Thiebert. (00:26:30)
Revealing mistake: When Humphrey checks out of the mail from the dating website at the end of the episode, behind the window of the mail client, there's a fingerprint file with the name "Adam Frost" and a 2014 sampling date; it's a file recycled from two seasons before, 3-4. (00:49:55)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.