apparently the romans brought a lot of sarmatians to england during the roman empire. So the reason they are so swarthy looking is not because of celtic genes its because they are all Iranians.

If that were true, it would show up in the British DNA studies in the form of aberrant extra-West Asian admixture compared to other Northern Europeans.

People try to come up with weird theories to explain the ocassional weird phenotype among European populations. Britons and Irishmen with dark hair and eyes are not necessarily the offspring of some peculiar ancient or medieval migration to the archipelago.