Ethnicity is not based on genetic purity. The very name "English" originated from the invading Angles, and then the Saxe. They didn't invade an empty land. They invaded land inhabited by Celtic Britons. But being Celtic is a group defined by linguistics, and not DNA. Among that population were Romano-Britons, Iberians, Gauls and Germanic tribes. One of the features of the Ancestry DNA test is you can download your "sequence" and upload that to other platforms drawing upon different pools. So apparently I have a match to some poor Iron age bugger they dig up in Bedfordshire, but also from a dig in Prague, and one over on the shores of the Black Sea. So, I'd say, there is a bit of a Romano-Briton in me. Now, we can't argue that all European people are much the same; the British Isles had been separated from the European continent to achieve a genetic distinctiveness, thanks to the smaller gene pool. So, being English, based on "ethnicity" is a moving definition, depending on the degree of bastardisation that has occurred. Or, its meaningless, given that a sense of being "English" is actually a modern construct. Before "Englishness" was created, my ancestors might have been Middle Sax, or maybe Iceni, or was it the Briganti. Ironically we throw away those native ethnicities in favour of embracing an invading ethnicity, the proponent now moan when its not ossified. In the 21st Century, Englishness is based around culture and upbringing, and civic belonging, with the invading ethnicity receding. It, like Britishness, is actually whatever you want it to be. The English don't yearn for anything like the reunification Germanic people. There are some, mostly Mosleyites, who see Englishness something like Teutonic values, but that German nationalism was ultimately because of small man syndrome.
