The Anglo-Saxons were German, though, weren't they?!
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the Anglo-Saxons were not a single people. you mean the Angles and the Saxons, not forgetting the Jutes, who had a significant level of migration to the British Isles. Alfred the Greats mother was descended from Jutes. oh and the Frisians came across in small numbers. Then the vikings came, followed by the Normans. i would be amazed if there is a single person in the world who is 100% genetically descended from the 'Anglo-Saxons' and no other group/culture.
England has been shaped by the various migrant groups which come here and will continue to.