It may well have been at Castell Harlech that he was formally crowned Prince of Wales in the presence of envoys from Scotland, France and Spain.
Mae'n ddigon posibl mai yng Nghastell Harlech y cafodd ei goroni'n ffurfiol yn Dywysog Cymru ym mhresenoldeb llysgenhadon o'r Alban, Ffrainc a Sbaen.