Coel Hen appears in the Harleian genealogies and the later pedigrees known as the Bonedd Gwŷr y Gogledd (The Descent of the Men of the North) at the head of several post-Roman royal families of the Hen Ogledd [REF].
Judging by the genealogical references, Coel Hen must have controlled a large part of the Hen Ogledd.