Was King Arthur a Glaswegian?

The title is straight out of the Daily Mail, but bear with me.


Arthur is mentioned just four times in ancient Welsh literature:


Arthur's twelve battles are mentioned in Nennius' Historium Brittaniae.
The Battle of Badon is also mentioned in the Annales Cambriae.
Taliesin's The Spoils of Annwn mention Arthur in passing.
And "he was no Arthur," is the entirety of the fourth mention, in Y