So,I’m trying to do some research into the Arthurian Mythos as a Whole and I’m wondering when exactly the first Written Story/Account of King Arthur and His “Knights of the Round table” Began.
I answered a similar question here, on the oldest Arthurian texts. "Published" is a tricky word in a medieval context; if you mean "printed," the earliest printed Arthurian text in English was Malory's Le Morte d'Arthur, printed by William Caxton in 1485. This is predated on the continent by an edition of Wolfram von Eschenbach's early 13th c. Parzifal, printed in 1477; there may be some even earlier continental outliers that I'm missing. Let me know if I can provide any clarifications or follow-ups!