Geschichte Mitteldeutschland 2.0 » English people

Hello , England had been invaded several times by different people, After the Britons, the Roman arrived and had been there for 4 centuries, they created a Roman-Breton society with a mixture of people from Italy , soldiers, and natives , When the Romans left, though in books its always depicted like the whole Roman Population left too leaving only Britons and like if the country got back to beeing celtic only and with a celtic language, but according to what I have read around they already spoke a romanlike tongue . Plus in Britain the uncovering of roman towns and villas is continuous.
When the Angles , Iutes , Saxons arrived though I also read that they made an extermination of the whole population replacing it with themselvesand leaving no trace of the Romano-bretons, is that true or is a far fetched statement? How ispossible that they replaced completely the local population? As a prove they brought up the genetic differences between people from Wales and the rest of England , but weren't people from wales the least romanized and the ones that indeed remained more celtic still? Isn't more plausible that Romano bretons mixed with the Anglosaxons forming a new society and ethnicity?


I didn't find the right solution from the internet.
References:
http://h istorum.com/european-history/127701-english-people.html

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