‘It cannot be doubted’, she writes to her father à propos of the unspeakable De Puebla, ‘that nothing contributes more towards the prosperity or adverse fortune of kingdoms than the sufficiency or incompetence of ambassadors.’ Her interest was practical as well as theoretical. She had, she wrote to Ferdinand’s all-powerful Secretary, Almazan, ‘deciphered the last despatches without any assistance’. Now she ‘wishes she were able to write in cipher’ herself. Could she have the keys? Ferdinand had heard this easy authority once before from a woman. It was from his wife, Isabella. He responded in the same way. Picking up a hint from Henry VII, who had told him that he ‘liked to hear [his news] from her [Catherine] better than from any other person’, he decided that, in the interim before a new ambassador could be sent to England from Spain, Catherine herself should act as his envoy. She was sent credentials in form to present to Henry VII while De Puebla was instructed to share all communications with her. It would be difficult to imagine more uneasy bedfellows. Catherine, starved of purposeful activity as well as affection, threw herself into the new task. She presented her credentials to Henry VII. She started to write in cipher (braving, as she said, the laughter of Almazan and her father). And, above all, she learned the black arts of diplomatic deceit and double-cross. There was ample scope for these in her principal mission. This was to negotiate another dynastic marriage between England and Spain. The groom was to be her father-in-law, Henry VII, and the bride Catherine’s own sister, Juana. The English King had been a widower since the death of Elizabeth of York in 1503, while Juana had been widowed three years later in 1506, when the King-Archduke Philip had died shortly after arriving in Spain to take possession of his wife’s kingdoms. Juana was the beauty of the family and Henry VII, always susceptible to feminine charms, had been much smitten by her when he had briefly seen her at Windsor en route to Spain. That she was mad, or at least mentally unstable, counted for little. That she was young enough to be Henry VII’s daughter counted for less. Nor was Catherine herself squeamish or scrupulous. Instead, she saw such a marriage simply as a device which could redress the balance of diplomatic forces between England and Spain. At the moment, these were wholly in Henry VII’s favour. Ferdinand was eager for Catherine’s marriage to Prince Henry; Henry VII was indifferent if not hostile. If, however, Henry VII wanted, or could be made to want, to marry Juana, then an obvious quid pro quo suggested itself. Catherine, forced for so long to play a merely passive role, rejoiced in this opportunity to turn the tables. ‘I bait [Henry VII] with this [the marriage with Dona Juana],’ she proudly told her father. Miraculously, her own treatment improved, which she pretended to take at face value. She even pretended to be happy with De Puebla’s conduct of affairs: ‘I dissimulate with him [her letter to Ferdinand continued] and praise all that he does. I even tell him that I am very well treated by the King, and that I am very well contented; and I say everything that I think may be useful for me with the King, because, in fact, De Puebla is the adviser of the King and I would not dare to say anything to him, except what I should wish the King to know.’
Catherine had already implored her father to send a new ambassador, someone who was straight-talking and, preferably, had experience of England. This, she explained, was a country ‘remote from all others’ and with such strange forms of behaviour that it needed special treatment. Soon the credentials naming the new ambassador chosen by Ferdinand arrived. Who could serve his interests better than a loyal, loving and noble subject already living in London and with excellent access to Henry VII? Catherine herself was to be his ambassador.
It was an extraordinary move on Ferdinand’s part. Women, however high their status, were rare in the world of power and diplomacy. She was joining a select group of sixteenth-century women, most of whom owed their position or their power to blood ties or marriage. Perhaps Ferdinand, like others, saw something of her mother in Catherine. She was instructed to work in parallel with the increasingly sickly De Puebla – who had to be carried to court in a litter. Catherine presented her credentials to Henry VII early in the summer of 1507.
Catherine may have had more of a role in fixing her own marriage than we know. Her father certainly trusted her to carry out her own negotiations. ‘Shortly before the other king died you said that his death would ensure your marriage,’ he reminded her. Now it was her task to prove those words true. ‘You must use all your skill and prudence to show what you can do, telling my envoy what he should do to swiftly close the deal.’ His instructions were not needed. The deal had been struck even before he wrote to her. Ferdinand was impressed. His daughter’s role in persuading Henry, he felt, must have been crucial. ‘I trust so much in your virtue and prudence that I not only leave to you the direction of your own affairs but would entrust the salvation of my soul to you,’ he told her.