<<The English royal family declare their descent from King David primarily from
THIS southern-route diaspora, although they have other Jewish descents from the "continent" of Europe.>>
The English / British Royal Family has never claimed or declared that they are descended from King David. This is an idea put around by groups like the British Israelites, who also follow an extra Biblical book, the Gospel of Nicodemos.
There is no historical evidence for this or the idea that most Europeans are actually Jews from the so-called Ten Lost Tribes. Wasn’t this also taught by the late Herbert W Armstrong from the Worldwide Church of God, which was quite heretical in many ways.
Doesn’t Paul or one of the other letter writers in the NT say that when we get away from the pure gospel we will start believing myths?
Stick to the Bible and stop reading all these other things written by men, usually with an agenda, and most of all forget conspiracy theory sites they really lead people astray. Also read the writing of the very early Christians such Early Christian Writings [Penguin Classics], that include the Letters to the Churches of Ignatius of Antioch, and others. They are called “The Apostolic Fathers” because they lived immediately after the Apostles, some of these fathers may have known the Apostles when they (the fathers) were young and the Apostles were old.
The Confessions of Augustine is very good book for Christians to read. It shows that thinks haven’t changed much in 15 / 16 hundred years. When Augustine was 16 he discovered girls and sex, got involved with all the heretical cults of his day, lived unmarried with his mistress, became an unmarried father with her (his son died at 16). His mother Monica spent much time weeping and praying and asking church leaders to pray for her son, who eventually came to Christ and became one of the great men of Christendom. His father was a Greek pagan, and Monica prayed for him and the Lord rewarded her by both her eldest son and her husband coming to Christ before her death. Of course, there is much more than this in the book. Personally I prefer books written in the early days of Christianity to modern ones. There seems to be a much greater degree of sacredness and devotion to God than the modern ones, which often seem to be about making out lives better than concentration on God.