Your ancestors painted themselves blue and went into battle naked! They drank homebrew from the skulls of their enemies!
Those that painted themselves blue were beaten centuries ago by the Romans. The celts did burn down london under queen Boudicca
Boudicca, also spelled Boadicea or Boudica (died 60 or 61 ce), ancient British queen who in 60 ce led a revolt against Roman rule. Boudicca’s husband, Prasutagus, was king of the Iceni (in what is now Norfolk) as a client under Roman suzerainty.
Romans rallied afterwards and killed most of Boudicca's followers and suppressed for once all those that painted themselves blue in what became England. Haddrian's wall was sort of the northern limit to what was absolutely Roman.

Point is the english have been subjugated more than once and seeing what is happening should be no big surprise.