Edward hammered home his dominance by constructing four new royal castles at Aberystwyth, Builth, Flint and Rhuddlan.
Pwysleisiodd Edward ei oruchafiaeth dro ar ôl tro drwy godi pedwar castell brenhinol newydd yn Aberystwyth, Llanfair-ym-muallt, y Fflint a Rhuddlan.