Oaths of Britain
The part of 12th century Britain we’re going to be playing with is the remains of Roman Britain. You can read up on this on Wikipedia, but essentially, the (Celtic) Britons were on that land from the Iron Age. The Romans invaded in the 1st century AD and generally settled down to be nice civilized, liberal, accepting Romans-gone-native. The (Germanic) Anglo-Saxon invasions swept away much of the Britons’ legacy, but their inability to conquer Wales (or Scotland. Or Ireland) left a significant Celtic presence on the island. The Norman invasion in 1066, however, did its best to impose Norman French culture on the island and obliterate everything that was already there.
Our story will be nominally centered on Wales, specifically Isca Augusta (Caerleon), but characters are welcome to be based in any historically Briton settlement or city. Bear in mind that for “Britain” I mean the British Isles as a whole, because “Oaths of Great Britain, Ireland, and the Channel Islands” just takes too long to write. Brittany is also an option, if the spirit moves you in that direction, but I’d like a reasonable background tie to England to be part of that.