The Welsh are pretty swarthy, they apparently have more Indo in their Indo-European DNA.
There's a dyke ( Offa's Dyke) that seperates Wales from England.
(Offa's Dyke (Welsh: Clawdd Offa) is a large linear earthwork that roughly follows the current border between England and Wales. The structure is named after Offa, the Anglo-Saxon king of Mercia from AD 757 until 796, who is traditionally believed to have ordered its construction. Although its precise original purpose is debated, it delineated the border between Anglian Mercia and the Welsh kingdom of Powys.)
Many don't know about this dyke. Also, I've read the the world's highest concentration of O type blood is in Wales.
Most of the DNA in Wales has its origins in the Iberian Ice Age refuge.
None of the Welsh actors & actresses, that I can think of, are swarthy at all. But then, these are the only Welsh people whom I know what they look like.
Richard Burton, Anthony Hopkins, Ray Milland, Ioan Gruffudd,Hugh Griffths, Stanley Baker, Glynis Johns, Catherine Zeta-Jones,Dawn French, Sian Phillips, for example.
My grandfather was Welsh and not particularly swarthy. I wonder if some of this swarthiness might be similar to the “black Irish” who have blood from men rescued from the sinking Spanish Armada who married good Irish Catholic girls. The Welsh were not that fond of the English, and may also have rescued Spanish sailors. In fact, the name Williams, common to the Welsh, is a contraction of “William’s man” as the Welsh welcomed William the Conqueror as he conquered the Britons.