For a start, the concept of a "Celtic" people is a modern and somewhat romantic reinterpretation of history.

The Britons also retained control of Wales and Kernow (encompassing Cornwall, Dartmoor and the Isles of Scilly) until the mid 11th century AD when Cornwall was effectively annexed by the English, with the Isles of Scilly following a few years later, although at times Cornish lords appear to have retained some sporadic control into the early part of the 12th century AD. The language eventually began to diverge; some linguists have grouped subsequent developments as Western and Southwestern Brittonic languages.

The Britons (Old English :Bryttas, Welsh : Brythoniaid, Cornish : Brythonion, Breton : brezhoned) also known as Celtic Britons or Ancient Britons, were indigenous Celtic people who inhabited Great Britain from at least the British Iron Age into the Middle Ages, at which point their culture and language diverged into the modern Welsh, Cornish and Bretons (among others). Unter Britonen oder Inselkelten (griech. The foster father many times was the brother of the birth mother. Britons or Brythons or British people were not the original inhabitants of what we call England today, but they were certainly one of the earlier peoples to inhabit what we call England today. Deifr (Deira) which encompassed modern day Teesside, Wearside, Tyneside, Humberside, Lindisfarne (Medcaut) and the Farne Islands fell to the Anglo-Saxons in 559 AD and Deira became an Anglo-Saxon kingdom after this point. Many years ago during ancient Greek times, Pytheas called these northern islands collectively, ai Bpettaviai (hai Brittaniai) which has been translated to the Brittanic Isles. Many of the hill forts were built on top of earlier causewayed camps.

Their culture and history was passed down verbally from one generation until another. The Romans have left written record of human sacrifice as being part of Celtic life. Northwest Europe was dominated by three main Celtic groups: the Gauls (in France), the Britons (in England) and the Gaels (in Ireland). Trade was essential during the Bronze Age, for not every area was naturally endowed with the necessary ores to make bronze. [37] The six examined native Britons all carried types of the paternal R1b1a2a1a, and carried the maternal haplogroups H6a1a, H1bs, J1c3e2, H2, H6a1b2 and J1b1a1.

Thirty years or so after the time of the Roman departure, the Germanic-speaking Anglo-Saxons began a migration to the eastern coast of Britain, where they began to establish their own kingdoms, and the Gaelic-speaking Scots migrating from Dál nAraidi (modern Northern Ireland) did the same on the west coast of Scotland and the Isle of Man. Common Brittonic was a Celtic language spoken in Britain and Brittany.

Welsh native history states that the island was named after Brutus of Troy, a Trojan prince cast into exile (See: Historia Brittonum by Nennius, and Brut y Bryttaniait ‘Chronicle of the Early Britons’ as annotated and translation by Wm R Cooper MA, PhD, ThD). The southwestern area’s dialect became Cornish in Cornwall and Breton on Gaul (France). These were often small ditch and bank combinations encircling defensible hilltops.