I remember seeing a kids programme which told of trousers being invented by one Jacob Trouser during the 19th century. They were apparently championed by the Duke of Wellington who found them ideal for wearing (rather than britches) when on horseback.

Oddly enough, I don't see all that many people riding to the office in the morning on the M25 (London orbital road). But inertia and programming keep most folk in trousers..