That I did know. Growing up in the early 70's the Old Man had a couple of 33/34 Box Saloons (as the rather good looking example above). The Austin 7 club at that time used to delight in telling this story.
One bit of folk lore I'm not sure if it was true (I was only little), to make it left hand drive all they did to that first car was mirror image the plans. But the side effect of that was, all the threads reversed, so left hand became right hand or vice versa. Which meant parts may look like they were interchangeable, but werent.
Does anyone know if that is true ? Or an urban legend told to fascinate a little kid . . . ?