...Many men wonder about this Arthur, whom Geoffrey extols so much singly, how the things that are said of him could be true, for, as Geoffrey repeats, he conquered thirty realms. If he subdued the king of France to him, and did slay Lucius the Procurator of Rome, Italy, then it is astonishing that the chronicles of Rome, of France, and of the Saxons should not have spoken of so noble a prince in their stories, which mentioned little things about men of low degree. Geoffrey says that Arthur overcame Frollo, King of France, but there is no record of such a name among men of France. Also, he says that Arthur slew Lucius Hiberius, Procurator of the city of Rome in the time of Leo the Emperor, yet according to all the stories of the Romans Lucius did not govern in that time - nor was Arthur born, nor did he live then, but in the time of Justinian, who was the fifth emperor after Leo. Geoffrey says that he has marveled that Gildas and Bede make no mention of Arthur in their writings; however, I suppose it is rather to be marveled why Geoffrey praises him so much, whom old authors, true and famous writers of stories, leave untouched.
...But perhaps it is the custom of every nation to extol some of their blood-relations excessively, as the Greeks great Alexander, the Romans Octavian, Englishmen King Richard, Frenchmen Charles [Charlemagne]; and so the Britons extolled Arthur. Which thing happens, as Josephus says, either for fairness of the story, or for the delectation of the readers, or for exaltation of their own blood.