Why did the British and other Euro Armies typically wear holsters on the left?

Later note: this vid is overly simplistic. The one at the link is more specific and better, dealing with Brits in WW1 specifically: In another Unexpected Video, The Bloke takes a look at the whys and wherefores of that peculiar (but not universal) old habit of wearing a pistol holster on the left that infested not only the Continentals, but also the British Army in the WW1-WW2 period and beyond. Being The Bloke, he of course gets a little dressed up to do it. He just can’t quite resist. May also contain traces of contortionism. Such things might be at least vaguely interesting what with the release of Battlefield 1 and all that... Like our FB page!