Many of the self identifying 'white" people are of English descent. Now, even if you can trace your lineage 10 generations back, England is mixed.

it is a mixture of Celts, Germans, Romans, Vikings, and anyone else the Roman Empire could import. They did a lot of that, because,according to Cicero, the Britons were too stupid to be trained as slaves. Oh yes, this does cover all of that Saxon vs Norman stuff they mentioned in Ivanhoe, as the Saxons hates those uppity french Viking Normans that conquered them in 1066.