Analysis
The story resembles Geoffrey Chaucer's "The Squire's Tale" from the Canterbury Tales, the English romance Sir Launfal and especially the Carolingian romance Pèlerinage de Charlemagne, in which Charlemagne and his paladins visit the Byzantine Emperor, superior to Charlemagne in looks according to Charlemagne's wife. They make a series of boasts about their abilities, and are called out on them by the emperor's spy, but are eventually able to fulfill them with help from God. Making chivalric vows is a central theme in the medieval English tale The Avowing of Arthur, while the importance of keeping one's pledges is important to tales like Sir Gawain and the Green Knight and The Wedding of Sir Gawain and Dame Ragnelle.
"King Arthur and King Cornwall" may be a version of a lost medieval story, but it is also possible that it is a product of the 17th century, taking hints from older chivalric romance. The character of Bredbeddle makes the author's knowledge of The Greene Knight obvious; whether made in the 16th century or before, the ballad relies on the audience's knowledge of the Gawain romances popular since the 12th century. Gawain's promise to have his way with Cornwall's daughter is in accordance with his womanizing portrayal in certain Old French works.
The magician-king of Cornwall does not appear in other Arthurian romance. In other stories, Cornwall is ruled by either Arthur's cousin Cador, or by King Mark, the uncle of Tristan and husband of Iseult. Equally unique is Cornwall's daughter, whom he had fathered on Guinevere behind Arthur's back. Several Arthurian staple characters do make appearances, such as Guinevere, Gawain, and Tristan.
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