Henry VII planned to marry Arthur to a daughter of the Catholic Monarchs, Isabella I of Castile and Ferdinand II of Aragon, in order to forge an Anglo-Spanish alliance against France.
In a letter from October 1499, Arthur, referring to Catherine as "my dearest spouse", had written: "I cannot tell you what an earnest desire I feel to see your Highness, and how vexatious to me is this procrastination about your coming.