There was a programme on TV last week, possibly an old one, with Dr Alice Roberts, and the scientist bods of some university had done some DNA mapping. The gene pool was fairly limited, and indicated that the accepted "violent invading foreign hoardes" were no more than folklore and the genetic evidence was of mostly peaceful co-existence. There were geographic genetic differences, with Wales, Cornwall, being quite distinct to Central England, and a lot of commonality between Ireland, Scotland and Northumberland.