Ignoring immigartions of the last years....
Assuming James is Scotish, he is likely to be a different mix than an English man. The Germanic and Norman Influence, means I am more like current continental europeans than those (Welsh,Scottish and Irish) who would have been on the British Isle long before the later invasions. Although He will share with the Gauls
We both have a Viking influence, too espsicaly norther England.
So even without looking at recent immigration, We are a big mix of Continental Europe all in different ways.
Neaderthals that did exist in Britain were forced out during the last ice age and didn't return, so any Neaderthal DNA would have been derived from European Continentals, not from Neaderthals themselves.
Neadertal is in Germany btw, near Dussuldorf
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