SerendipityJane
England eventually overcame the Norman conquest so entirely that even the language of the invaders has been erased in the UK.
Apart from the thousands of words that haven't been, of course. (Possibly, according to some sources, as much as forty-five per cent of the language, though I am not at all sure about that. I would certainly go with thirty percent, though.) What English does is not replace words, but add new ones all the time whilst continuing to use the previous ones.
To use the classic example, food and the animals it comes from, we have beef, mutton, pork, veal, venison, pullet and pigeon, which all have Norman-Old French origins, as opposed to the Old English cow, ox(en), sheep, pig/swine, calf, deer, hen/chicken and dove.
see https://en.wikipedia.org/wiki/ListofEnglishwordsofFrenchorigin
And just to complicate the issue, some Old French words whose derivatives we still use came not from the Norman conquest but during the earlier Danish one, because the Danes were not above nicking words they found useful, and they had dealings with Old French and with Latin as well. Also, the Normans were not originally French; they were Norse. so their language was not originally French. Rollo, who founded their kingdom, seems very likely to have been born in western Norway. The Danes, naturally enough, say he was Danish....
In fact, it's practically a truism that the language of a conquering people takes over from that of the conquered; that is why English has so few Welsh words in common use in it.
https://en.wikipedia.org/wiki/ListofEnglishwordsofWelshorigin
Except, apparently, in Normandy, where they took to Old French.
Sometimes (as in Canada and Tibet and latterly in occupied parts of Ukraine) conquerors actively set out to destroy the language of the conquered and forbid its use. This seems not to have happened here in 1066.
In any case, a wise man (James Nicoll) once pointed out that "English doesn’t borrow from other languages. English follows other languages down dark alleys, knocks them over and goes through their pockets for loose grammar." One might also say that after a century or so such words (war, cot, caravan, bungalow, castle, forest, cat, apostle, dandelion, orange) become English, rather than English overcoming them.