Geoffrey ends by requesting historians, his contemporaries, such as William of Malmesbury, "to be silent concerning the "History of the Britons," since they have not that book written in the British tongue, which Walter, Archdeacon of Oxford, brought out of Brittany". This is mere open banter. Geoffrey was not likely to show them that book!
Even in the old Welsh tale of the great boar-hunt, a story far earlier than Geoffrey's time, Arthur is surrounded by many fabulous heroes, really characters of fairy-tale, like them who followed Jason in the search for the Fleece of Gold. All of them can do miraculous feats, like the heroes of "the dream-time," "the dark backward" of unknown ages. These companions of Arthur become, at least some of them do, the Knights of the Round Table in the later romances, but we do not yet hear of Launcelot, or of the Holy Grail.
From Geoffrey's book come the French poetical and adorned version of Wace (1155), many French romances, and finally a vast throng of chivalrous and romantic fancies cluster round the great name of Arthur. Geoffrey's was a book that gave delight to every one, ladies as well as men, for in the marriage of the traitor Modred with Guinevere the wife of Arthur, and in Arthur's revenge, was the germ of a world of romances. The conquest, too, by Arthur, of Gaul and Aquitaine, inspired, and, to their minds, gave an historical excuse for the ambition of English kings to recover these old dominions of Britain. Caxton, our first printer, long afterwards wrote that not to believe in Arthur was almost atheism.
Geoffrey also translated into Latin out of Welsh the prophecies attributed to the enchanter Merlin. If they had any meaning in Welsh, in Latin they have none. Hotspur, in Shakespeare's "Henry IV," is weary of Owen Glendower's talk
Of the dreamer Merlin and his prophecies,
And of a dragon and a finless fish,
A clip-wing'd griffin and a moulten raven,
A couching lion, and a ramping cat,
And such a deal of skimble-skamble stuff.
Nevertheless, three centuries after Geoffrey wrote, men who thought themselves wise and learned believed that not only Merlin but Bede were true prophets, who foretold the victories of Joan of Arc (1429).
It must be kept in mind that Geoffrey says nothing about these great characters in later Arthurian romances, Launcelot, Galahad, Tristram and Iseult, and nothing about the mysterious Holy Grail, and the Quest of the Grail. How and whence these parts of the Arthurian legend arose, how much of them comes from ancient Celtic legend, how much from the invention of French romancers, is still a mystery. Geoffrey, however, made Arthur, Merlin, Guinevere, and Modred familiar to all his readers. All Englishmen were proud of Arthur of Britain, though, of course; in his life he was the deadly foe of the English.