Driving on the left

Friends for Germany are visiting at the moment and I was driving them back to where they were staying after dinner last night. We were talking about how strange it was for them to be driving on the left - everything seemed out of whack.

I told them I had a dim memory of it being something to so with knights of medieval times passing each other with their sword arms (right arms) in the middle of the road. They were more of the opinion that it was just a hangover from the British Empire and a case of the British being bloody minded and not conforming to the norm.

A bit of investigation turns out we are both sort of right. About a third of the world drives on the left and they are mainly ex British colonies (Japan, which also drives on the left, being a notable exception). Back before 1800 or so pretty much everyone was thought to have driven on the left - although it isn't really known. There is evidence the Romans drove on the left. Then Napoleon came along and France and its conquests started driving on the right - allegedly because Napoleon was a left hander and wanted his sword arm in the middle - while this may not be true it is a good story.

So ex British Colony Australia drives on the left and ex Napoleonic conquest Germany drives on the right.