|Quoting 777Jet (Reply 70):|
It appears that the Prince usually sits on the right... I wonder if this is some kind of Royal protocol?
It isn't hard and fast - Charles sat to the left of Diana in their wedding coach, presumably to give her time to get settled with that vast dress - but generally the protocol is that the consort stands (or sits) to the left of the monarch, as at the State Opening of Parliament.
It gets a bit muddied when they are out and about - or in less formal settings. Prince Philip often sits to the right of the Queen at the Highland Games, for example, although his more usual position is to her left. It gets really muddled at some state banquets when the rank of the state guest's consort has to be considered.
In cars, it also has a more practical purpose - it's quicker for the driver to get to the right passenger door if there's no one else around to open it and the protocol is that the one on - or closest to - the throne has rank.
[Edited 2014-04-18 18:11:00]