John of Gaunt of Castile. As his father and elder brother, Edward, the Black Prince, became incapacitated due to poor health, Gaunt assumed control of many government functions, and rose to become one of the most powerful political figures in England. He was faced with military difficulties abroad and political divisions at home, and disagreements as to how to deal with these crises led to tensions between Gaunt, the English Parliament, and the ruling class, making him an extremely unpopular figure for a time. John exercised great influence over the English throne during the minority of King Richard II, and the ensuing periods
John of Gaunt dexter side of the shield (the left hand side as viewed), and the differenced English royal arms on the sinister; but in 1388, when he surrendered his claim, he reversed this marshalling, placing his own arms on the dexter, and those of Castile and León on the sinister. He thus continued to signal his alliance with the Castilian royal house, while abandoning any claim to the throne. There is, however, evidence that he may occasionally have used this second marshalling at earlier dates. In addition to his royal arms, Gaunt bore an alternative coat of "Sable, three ostrich feathers ermine".