And I thought that the Mad is the last remnant of the Tethys ocean caused by plate tectonics as Africa moved north towards Europe. This theory is as old as the hills and was replaced when plate tectonics came of age.

In Britain we use both systems. But you might be interested to know that some imperial systems are alive and well but under a metric camoflage. Pipes are measured in imperial, a world standard, (BSP) as is the thread on pipes imperial and both are accepted even in France! Unfortunately we can only buy pipes in metric here in the UK but in France you can buy in imperial. It is a mad mad world.