Article: During the war, plans were drawn up to quell Welsh nationalism by affiliating Elizabeth more closely with Wales. Proposals, such as appointing her Constable of Caernarfon Castle or a patron of Urdd Gobaith Cymru (the Welsh League of Youth), were abandoned for various reasons, which included a fear of associating Elizabeth with conscientious objectors in the Urdd, at a time when Britain was at war. Welsh politicians suggested that she be made Princess of Wales on her 18th birthday. Home Secretary, Herbert Morrison supported the idea, but the King rejected it because he felt such a title belonged solely to the wife of a Prince of Wales and the Prince of Wales had always been the heir apparent. In 1946, she was inducted into the Welsh Gorsedd of Bards at the National Eisteddfod of Wales.

Question: Who was the always the Prince of Wales?
heir apparent