Indeed, and having replaced the aristocracy they let the 'lower classes' carry on much as they had before, continuing with their existing customs and (lower lev

Indeed, and having replaced the aristocracy they let the 'lower classes' carry on much as they had before, continuing with their existing customs and (lower level) forms of governance - just with new 'top bosses' if you will. So in comparison to other places that did not have such a wholesale aristocracy replacement, this really cemented the class divide. No longer was the aristocracy 'like you but richer/more powerful', but quite different - different language, customs etc. 1066 was the last successful invasion of the British mainland, so, aside from the odd civil war, no sweeping 'cataclysm' occurred to shake things up. We didn't even have a revolution like the French, instead a gradual (over centuries!) transition to our current democratic system, with a constitutional monarchy (itself a remnant of the old ruling system).