Most likely Viking settlements and intermarriage, with no Anglo-Saxon dna influence.
DNA testing is going to change our thinking about family history.
Now 300 years later, John Smith from the USA gets a DNA test done. What does he find? He finds that his ancestry is French. Actually his ancestry is English but there is no trace of DNA in England of his actual English ancestry.
So what I'm saying is, how accurate is the resulting information of a DNA test as far as location is concerned if the majority of the Smith family was born and raised in France?