... Whether Lludd-dun or Luddon could have become Lun-dun is a difficult question, but since the Domesday Lodenesburg has become Londesborough, and the Pettalandfjörth is now the Pentland Firth, it is possible that Loden-dun or Lud-dun may have become Lundun or London. (Names and Their Histories, Taylor, 1898)

    Beli the Great, the son of Manogan, had three sons, Lludd, and Caswallawn, and Nynyaw; and according to the story he had a fourth son called Llevelys.  And after the death of Beli, the kingdom of the Island of Britain fell into the hands of Lludd his eldest son; and Lludd ruled prosperously, and rebuilt the walls of London, and encompassed it about with numberless towers.  And after that he bade the citizens build houses therein, such as no houses in the kingdoms could equal.  And moreover he was a mighty warrior, and generous and liberal in giving meat and drink to all that sought them.  And though he had many castles and cities this one loved he more than any.  And he dwelt therein most part of the year, and therefore was it called Caer Lludd, and at last Caer London.  And after the stranger-race came there, it was called London, or Lwndrys... (Mabinogion, Guest, 1910)