Cornish version in the poem translated by John of Cornwall into Latin hexameters during the twelfth century and entitled “The Prophecy of Merlin.” John claims he is merely translating from an earlier Cornish manuscript, and to help us he puts glosses of Cornish words in the margins. These forms certainly put the manuscripts back to the tenth century. The oldest surviving copy of this manuscript is dated October 8, 1474, and is in the Vatican Library. While the Cornish scholar Henry Jenner accepted this manuscript as genuine in 1903, he was referring to it as “a medieval fake” in 1913 [“The Tristan Romance and Its Cornish Provenance,” Journal of the Royal Institute of Cornwall, Vol. XVIII]. However, he does not declare his reasons for changing his mind, and so far there is no good explanation for believing it was a correct decision.

It must be remembered that the oral tradition of storytelling was as strong among the Brythonic Celts as it was among the Goidelic Celts. Like the Irish, Manx, and Scots, who had their seanchaidhe, or oral storyteller, the Brythonic Celts had their cyfarwydd. There was a constant intercourse of missionaries and teachers between Wales, Cornwall, and Brittany from the fifth century even into Tudor times. And while there was no literature in Breton before the fifteenth century, it does not mean there was none in oral form. The Breton lais, the stories of Arthur and of Tristan, shared with their cousins in Wales and Cornwall, were seized upon by Chrétien de Troyes (fl. 1160–1190), who wrote some of the earliest Arthurian romances; by Beroul, who wrote the oldest extant Tristan poem; and by Marie de France (ca. 1200), who admitted that she was adapting the poetic saga of the Breton bards.

However, the oldest text in Breton dates from the year 1450 and is Dialog etre Arzur Roe d’an Bretounet ha Guynglaff (The Dialogue of Arthur, King of the Bretons, and Guynglaff). Guynglaff or Gwnec’hlan was a druid and seer and the work is of literary curiosity, being a uniquely Breton contribution to the sagas. By the end of the fifteenth century, Breton literature started in earnest with Buhez santaz Nonn hag he map Deuy (The Life of St. Nonn, Son of Devy), a long hagiographic poem, setting a tradition for such works that continued up to the French Revolution. But there is nothing else that enriches our knowledge of the mythology shared with the other Celts outside of oral tradition. It was not until 1839 that Théodore Hersart de la Villemarqué published Barzaz Breiz: Chants populaires de