Oh, by the way, it is interesting that the study is of the Y chromosome, that is, it traces male lineages. The article mentions all major waves of invasion into the British islands.

I would venture that a study of mitochondrial DNA, which traces female lineages, would paint a different picture as it is easier for a predominantly male army to come, conquer and interbreed than for an entire balanced population to move into a previously populated area.

Those whom the Gods wish to destroy They first make mad. — Euripides