Episode #2.8 - S2-E8
Continuity mistake: In the scene with Richard bossing Camille around with his brisk finger-waving, she is pinning in place the red tape using just two fingers pointed against the book or her hand hovering on top of it, clenched in a fist, depending on the angle. (00:09:50)
Episode #2.8 - S2-E8
Continuity mistake: Richard lifts the soft paper towards the UV light picking it with his tongs by the far corner - in the close-up the strip is pinched right in the middle of it, though. (00:24:25)
Episode #2.8 - S2-E8
Continuity mistake: During the denouement, DI Richard Poole holds the evidence bag with the murder weapon showing it to his audience. The bag is held differently between shots, as the blue bands make easy to spot. (00:37:35)
Episode #2.8 - S2-E8
Continuity mistake: When the murder is shown, the killer grabs the gun with both hands at first, then the close-up shows them pick the gun from the drawer with just the left hand. (00:39:40)
Episode #2.8 - S2-E8
Continuity mistake: When the killer walks away from the victim, his right arm touches the carpet in the first shot, is above it in the next, and was even further distant from it in the one before the opening roll of the episode. (00:40:00)
Episode #2.8 - S2-E8
Continuity mistake: In the whimsical finale, Richard rips away from Dwayne's hands the envelope with the test results; the envelope switches side multiple times between shots - just look at the stampings and how they change position from cut to cut. (00:42:40)
Episode #2.8 - S2-E8
Continuity mistake: Fidel grabs the envelope with his results. Brief reaction shot on Dwayne and Poole, and suddenly the beer bottle and Best's cell phone have rotated. (00:43:00)
Episode #2.8 - S2-E8
Other mistake: Richard states that all 33 of the prints he recovered from the cash wraps were by the victim, but we see the secretary in flashbacks collect them from the garbage bin with no gloves, which would leave obvious prints that can't be washed away - the presence of prints wouldn't even be all that incriminating per se, since it wouldn't be terribly strange for the personal assistant to momentarily handle some money inside her boss' office.
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.