Bristol manuscript fragments of Merlin legend among the oldest of their kind
phys.org
phys.org
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So it puts parts of the Arthurian Merlin earlier but does not give an earlier root character?
on edit: link to wikipedia black book of carmarthen https://en.wikipedia.org/wiki/Black_Book_of_Carmarthen
The Merlin character didn't show up in literature for another 700 years, about a century after other Arthurian stories started showing up.
The entire set of Arthurian stories are a result of real histories in Britain after the Roman collapse and Celt and pagan myths being written down in the 1100's.
Because of modern memes and stories, it's hard to grasp how thoroughly the Romans obliterated any and all knowledge of druidic history. The notion of nature worshipping powerful shamans is a modern conceit, and doesn't match any of the known written or oral histories.
Romans went scorched earth on religions they didn't like, and there's probably a dozen or so cultures like the druids where all we have left is bits and pieces of hearsay and mythologies.
As far as I know the pre-Christian Roman Empire was very tolerant of foreign religions as long as they reciprocated by respecting the Roman religion. I'm not sure why Druidism would have been unique in that regard. Do you have any references supporting your assertions and explaining why Druidism would have been singled out among other pagan religions for persecution ?