Episode #1.4 - S1-E4
Stupidity: Richard is hellbent on proving what really happened, but he sits for more than a whole day on a vital piece of evidence (the phone), does not check it, and despite the fact that the victim was reported being in heated arguments with someone on the phone, he asked for no record of the calls (nor checked whose phone was it, which would have required simply inspecting the SIM card), which would have cracked the case instantly.
Episode #1.1 - S1-E1
Stupidity: The case is made to be this incredibly complex locked room murder mystery, but it is so simply because nobody did a routine check of the phone records of the suspects / one of the victims (if not of the cell tower of the zone). The detectives would have instantly stumbled upon a major unexplained contradiction, since an incriminating call was made.
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.