Steve Shaw has it right up there. I used to wonder, as a child, why America drove on the right when in all their films, their stagecoaches drove on the left. It was explained to me that everyone drove on the left in those days so that the driver could swing his whip right-handed.
Then there was that Napoleon bloke who took over most of Europe and ordered that everyone did everything to his way of thinking.
I wonder if HE was left-handed?