Celtics in Brittany: The Britons
https://www.history.com/topics/ancient-history/celts

Britons and Gauls settled in the northwestern corner of present-day France, the region known today as Brittany. The Celtic tradition survived in the region as it was geographically isolated from the rest of France, and many festivals and events can trace their origins to Celtic times.

Many of the French “Bretons” also wear traditional Celtic hats called coiffes (which means “hats of lace”), and roughly one-quarter of the region’s residents speak Breton, a Celtic language similar to Welsh.

Although Caesar’s invasion of Britain was unsuccessful, the Romans eventually mounted a successful attack against the Britons following Caesar’s murder in the first century A.D. This incursion effectively pushed the Britons on the island west to Wales and Cornwall and north to Scotland.

In fact, the Romans built Hadrian’s Wall (remnants of which still stand today) near what is now the border between England and Scotland, in 120 A.D. The wall was designed to protect the conquering Roman settlers from the Celts who had fled north.

Celtic Languages

In Wales, called Cymru by the Celts, the native tongue—Welsh—is a Celtic language, and it is still widely spoken in the region. In Cornwall (the westernmost county in England, and near Wales), some (although very few) speak Cornish, which is similar to Welsh and Breton.

And, in Scotland, the Celtic language Scots Gaelic is still spoken, although by a minority, and the local affiliate of the British Broadcasting Corporation (BBC) is known as BBC Alba, the Celtic name for the region.