Continuity mistake: In the scene in the National Gallery early on in the film where Bond meets Q, there is a line of bench seats. Bond is sitting on the end of one benches looking at a painting. The shot is from behind. Q comes and sits on the adjacent bench next to Bond. You can see the gap between the two benches between the pair. Then the shot changes to a front view as they start talking. But suddenly there is no gap in the bench in between them, they are both sitting on the same bench, the gap is now to Bond's left.
Picture added by ployp