Four minute mile

This morning I managed 8 minute miles so Roger Bannister was twice as fast as me. There are 15 lots of 4 minutes in an hour so he must have been running at 15 mph. I looked up the history of the mile as a unit of measurement https://en.wikipedia.org/wiki/Mile I knew it started with the Romans but I hadn't realised it was linked to furlongs, a distance I only know from horse racing but which apparently was how far oxen could pull a plough before needing a rest.