Try to find out if King Arthur really existed, it is possible for the documentary sources - books, letters and poems. But they are known, are not always easy to interpret. It is pleasant, of course, be considered impartial historical documents, but it is not. Even today, reading about current events in the world, we realize that we are invited to only one of the possible points of view. And when driving backwards into the past, to recognize the bias is even more difficult, because the entire available range of opinions and observations are preserved only fragmentary, scattered in time.