The records of this era are scanty, and Idwal's name appears only in the pedigrees of later kings and in a prophecy found in two 14th century Welsh manuscripts, which says that he will succeed his father Cadwaladr as king.
The only mention of Idwal Iwrch in the historical record is the appearance of his name in genealogies such as those from Jesus College MS. 20 (as the father of "Rhodri Molwynog son of Idwal Iwrch son of Cadwaladr Fendigiad")[2] and the Harleian genealogies (as the father of "Rotri son of Intguaul son of Catgualart").
[3] John Davies'; History of Wales does not mention Idwal,[4] while John Edward Lloyd's History says only that Idwal was Rhodri Molwynog's father.
Idwal's name appears in the Dialogue between Myrddin and his sister Gwenddydd (Welsh: Cyfoesi Myrddin a Gwenddydd ei Chwaer), a Middle Welsh vaticinatory poem whose text is preserved in two medieval Welsh manuscripts, Peniarth 3 (c. 1300) and the Red Book of Hergest (c.
[6] In the text's question-answer form, a succession of "future" kings is prophesied, with Idwal among them.