When you colonize enough places all over the world, you tend to pick up things, and people.
I'm not sure Britain actually became a diverse society: I think it's always been that way.
Consider their history. The ancient Brits were a diverse lot, comprising many tribes and groups. Then the invasions started and they never had a chance to consolidate. So the British stock was fleshed out by the Vikings, Normans, Saxons … Read more