If, then, there was any disagreement between the King and his eldest son, it must probably be referred to the earlier part of 1412. It is easy to make conjectures about the cause, for indeed several causes are possible or even probable, but difficult to find reasons for preferring one conjecture to another. There may have been the ordinary jealousy that is found so often between the possessor and the heir of power. The elder Henry’s capacity may have begun to fail him, as his health certainly failed, during the last years of his life. Dissatisfaction on the side of the vigorous successor to the throne and suspicion on that of its enfeebled holder would naturally follow. And the young Henry may well have felt some personal annoyance at the tortuous policy which his father persisted in following in French affairs. The King made a treaty with the King of France in December 1410. No sooner was it proclaimed than in the following March he began to negotiate with the Duke of Burgundy, and concluded a truce with him in May. In the following year an alliance, offensive and defensive, was made with the French Princes who were acting on behalf of the then disabled King; and again, a month after this, another treaty was concluded with the Duke of Burgundy. The affairs of the Prince himself were one of the subjects dealt with in these negotiations. Henry the Fourth was eager in the extreme to strengthen his position by a matrimonial alliance with a royal family of undoubted title. It was now a daughter of the French King, and now a daughter of the Duke of Burgundy, who seemed to him a desirable bride for the heir to his crown; and it is just possible that the young man, who was quite capable of being resolute in such matters, did not wholly approve of the diplomacy by which his father sought to dispose of him in marriage.