In the letter J.R.R. Tolkien wrote to Milton Waldan, he wrote:
Also – and here I hope I shall not sound absurd – I was from early days grieved by the poverty of my own beloved country: it had no stories of its own (bound up with its tongue and soil), not of the quality that I sought, and found (as an ingredient) in legends of other lands. There was Greek, and Celtic, and Romance, Germanic, Scandinavian, and Finnish (which greatly affected me); but nothing English, save impoverished chap-book stuff. Of course there was and is all the Arthurian world, but powerful as it is, it is imperfectly naturalized, associated with the soil of Britain but not with English; and does not replace what I felt to be missing. For one thing its 'faerie' is too lavish, and fantastical, incoherent and repetitive. For another and more important thing: it is involved in, and explicitly contains the Christian religion. For reasons which I will not elaborate, that seems to me fatal. Myth and fairy-story must, as all art, reflect and contain in solution elements of moral and religious truth (or error), but not explicit, not in the known form of the primary 'real' world. (I am speaking, of course, of our present situation, not of ancient pagan, pre-Christian days. And I will not repeat what I tried to say in my essay, which you read
What did he mean that the legend of King Arthur was associated with Britain but not with English? Did he mean the English language? Did he mean King Arthur was not written in English originally?