Hi Roxana,
There is more to it than that, if one starts looking at where Vortigern had his probable powerbase and who Gildas's patrons were...
However, I prefer to apply Occam when it comes to Arthur. We have no contemporary reference to him. The only contemporary text is a polemic on the decline of Britain at the hand of its rulers. If Arthur should have been mentioned anywhere then it would be in such a document, either to be condemned or to be held up as an example. The absence of his name, coupled with the naming of a man who meets the criteria of the legend (a Roman uniting the warring Britons to defeat the Saxons, only to see the whole lot fade into internecine warfare) seems to me to be pretty conclusive. The simplest explanation wins based on the evidence that we have.
Pete
God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!