Firstly, the Scots and Welsh have always been British. Great Britain refers to the larger community, as distinct from Brittany in France (Le Petit Bretagne), where a form of Welsh is still spoken by a few. The term Great Britain has nothing to do with the Empire.
Secondly, before an American derides the British, he should remember his roots, unless he really prides himself on the Hispanic and Black component. OK there were lots of Germans, but in genetics and culture they are virtually the same as the English and are superior in many ways.
Thirdly, those of you in the USA do not have to support with your hard-earned cash the Afghan scum flooding into the UK, impoverishing it and ruining the public services, education, health and law and order.
Lastly, in the case eg. of the Turks, the UK is overflowing with so-called Kurdish refugees claiming to have been tortured by the Turkish police, who incidentally do a much better of job of cleaning up terrorists than do we in the UK. I need more than a blonde, however attractive, to persuade me that this guy is really what he claims to be.
Well, one only need look at Scottish people and see that genetically they are not the same as English people, who have much more admixture from Germanic peoples, specifically those of the area now known as Jutland. For you to say that all these people share the same genetics is fallacious, and science would not support it.
The word "British" has meant many different things, originally referring to the Celtic inhabitants of the Island. As the definition changed over time, you wold have me believe that the genetic composition of people changed to be congruent with the language.
According to your logic, the royal family is not genetically British because they are more German than anything, as evident through their family history.
Secondly, I am not American, but your claim that Americans should remember their "roots" in Britain is comical, as the people who started America came purposely to leave behind the moral and spiritual vacuousness of Great Britain. The men who started the U.S. were the first AMERICANS, and wanted nothing to do with their old country.
Lastly, I do not care whether or not this guy is let in, and that is not the argument I was making. If you don't want to let him in, fine, but do not use pseudo-science regarding genetics about your argument.
If only genetic British people are welcome in Britain, what then should we make of British Jews, or according to you, "Jews who happen to live in Britain until we make them leave with all the other people who are not genetically British"?