Neanderthal would be stretching the point a little, perhaps. Back when I was a student, opinion was that the Basque language was a neolithic survival (it is related to no other known language). The British Isles have been inhabited continuously since at least the neolithic period, and, given the relative geographical isolation of the two areas, it would not seem unreasonable that there might be an identifiable genetic link, significant parts at least of both deriving from aboriginal, pre-Celtic populations. Britain adopted Celtic languages and cultural practices (though, it begins to appear, not a great deal of any "Celtic" genetic inheritance) well before written records began, however. The megalithic artefacts that still cover these islands pre-date any Celtic influence.

It is largely a fallacy to suppose that "the Celts" were driven into the West by invading Germanic tribes; the continuity of place-names throughout what is now England suggests that there was rather less movement than used to be thought, and that the linguistic separateness of Wales and Cornwall reflects simply the fact that the new immigrants (and the Romans, for that matter) just didn't get that far. For what it's worth, red hair in my family seems to come from the "English", not the "Scottish" side; and the French idea of a "typical" Englishman is of a man with a pin-stripe suit and umbrella and red hair and freckles.

Who are the Welsh, then? The descendents, as most of us are, of the varied aboriginal inhabitants of the British Isles, who have sometimes adopted, and sometimes absorbed, the languages and customs of a whole series of immigrant groups over the centuries. We are a mongrel race in Britain, made of quite a mixture ("the gutter-sweepings of Europe", somebody once said) and all the healthier for it, I suspect.

The more I learn about the history and traditional culture of these islands, the more irrelevant and fatuous appear the modern, romantic attempts to separate us into isolated racial or national groupings. Simple regional groupings are another matter, perhaps; one town or village will always want to be different, and better, than its neighbour, and it is perfectly natural for recent immigrants to wish, for the time being, to remain separate. Separateness gives way, in time, to a commonality that still recognises distinctness. We have different patterns, but are all, in the end, made of the same cloth.