 Edward was determined to prevent any further rebellion in North Wales and set about building a sequence of new castles and walled towns , replacing the old Welsh administrative system with a new principality governed from Caernarfon . Dolbadarn was no longer relevant and within two years timber from the castle was being used by the Normans for the construction of Caernarfon Castle . This was both a practical and a symbolic action , demonstrating Norman power over one of the most important possessions of the Welsh princes . 
