'Indigenous Brits' are associated with the Celts - Scotland, Ireland and Wales. The Celtic Migrations spread from deep in the heart of Europe. The edges of where the Celts roamed is where the language legacy is most likely to be found now. Far from the core. The Gauls were also Celts. Germanic tribes pushed those who didn't assimilate out. The Germanic Franks formed the Kingdom of France after the fall of Rome (which held Gaul from 51 BC till 486 AD). The Angles and Saxons pushed onto the British Island. France emerged as a modern power during the Hundred Year War (1337-1453). The 16th Century was dominated by Religious Wars between Catholic and Protestant. The 18th Century saw the overthrow of Monarchy and the 'declaration of rights' . The 19th Century the Napoleonic Wars, and Empire building within Europe and Colonialism around the world.
Yellow (C6th BC); Light Green (By 275BC)
Dark Green (Areas where Celtic Languages remain widely spoken)