Analysis of information sources in references of the Wikipedia article "Historia Brittonum" in English language version.
It has often been suggested that Arthur's campaigns derive from a battle-catalog-type poem in Old Welsh, of the kind which survive praising King Cadwallon of Gwynedd. That some of the battle names rhyme (Dubglas/ Bassas; Celidon/Guinnion) might be thought to support this hypothesis. Even so, there seems little likelihood that this poem—if it ever existed—was written close to the events by someone who was well-informed. Wars do not as a rule feature rhyming battle-names, so this looks like poetic licence.