Oppenheimer??? curious way of thinking!
official History distords things but does not imagine them - I 'm a bit tired with the huge number of extravagant theories that come under light(with great regularity it's true) trying everytime to kill definitively "the father" and the official theories: we can try to correct them, but it is of no worth trying sweap them completely, the baby with the bath water...
for me it is evident that the most of the Y-I1, Y-R-U106 and Y-R1a came to the Isles with germanic tribes of any sort, and that the most of the most of the other Y-R1b are of celtic origin and maybe, some of them (it is debated) reached the Isles before the Celts - we can argue for details but the game is over, I think - even in details, we see a little bit more Y-R1a (and sometimes of Y-Q) in the Vikings settlements areas and more Y-R-U106 in the continental germanic areas - and England is not a block, no more than Scotland: and the regional distributions confirm and do not infirm these conclusions - as said by a forumer here, Y-I1 is very typical TOO of the continental germanic settlements, and not only of the Vikings ones - (the subclades confirm it) -
concerning Y-R1b-L21, it is now typical of Ireland, but is too very strong in other dense celtic settlements areas of the Isles
and it is yet strong enough in Brittany and N-W France, and present in some others areas of Europe, not only northern ones, but also in Basque Country (new surveys would give about 18% as a mean, but I don't know if it is the relative % witihin R1b or an absolute % in the total population, but knowing that Basques have almost 90% of R1b...) -
it is true that some North-Western I-Ean (see river old names) or nearly "germanic" small tribes could have put a foot in the Isles before La Tène Celts but they were not the providers of the whole eastern germanic population of Britain -
along with earlier Celts - as a whole all these Y-R1b don't show an ultime origin in Iberia, rather in E-France and around -
what is true also is that these %s concern only Y haplogroups that knew at evidence some super-evaluation by the fact they were the Y-HGs of the male elite - so the % of these Y HGs do not reflect genuinely the autosomals distributions, but here too, we can see that physical aspects reflect(ed) differences in distribution in the Isles, not surprising when looking at History - we have also the skeletons at different times in different places that show clearly the Isles were not an inaccessible sanctuarium -
(skeletons concerning 'Long Barrows', 'Bell-Beakers', 'Food vessels people', 'Urnfield Celts', 'La Tène' Celts and diverse Brittons, Roman Londoniers , Anglo-Saxon settlers, + ancient Y-HGs of Vikings settlements in the Liverpool Area and in other places) -