On the 11th of June Charles and Henry VIII traveled to Windsor Castle. They stayed there for nine nights until they departed on the 21st, setting for Farnham.
The first four days on Windsor were uneventful. On the 16th things became more interesting when the two monarchs discussed the terms of the treaty between Spain, the Holy Roman Empire and England. Although this meeting was merely a formality since the treaty was published that same day.

On the 19th, Henry and Charles got straight to business, and discussed another matter and signed another treaty.
“This one was to remain secret” Patrick William wrote in his biography on Katharine of Aragon, “for it committed them to the marriage of Charles to Princess Mary within eight years.”
In her biography on Mary I, Linda Porter explains that this marriage treaty stipulated that in the event that Katharine and Henry had no sons by the time this marriage came to be, the couple’s eldest son would inherit Henry VIII’s crowns, thus becoming King of England, lord of Ireland and King of France (in theory). In turn their second son, or daughter (if they couldn’t have any more sons) would inherit Spain and selected territories Charles ruled over.
Thirdly, since Mary and Charles were related in the second degree of affinity, the two monarchs would ask the pope for a special dispensation. And lastly, the matter of her dowry was settled and Charles promised that he would stay true to his betrothed and honor every part of the treaty.

On the 20th, Cardinal and Archbishop of York, Thomas Wolsey, convened a legatine court and asked the two monarchs to reaffirm their agreements with one another over the marriage treaty. The event had many important witnesses, among them Henry, Count of Nassau, Imperial Chancellor Gattinara, Pedro Ruiz de la Mota, Bishop of Palancia, Thomas Ruthall, Bishop of Durham, the Earls of Shrewsbury and Worcester, George Talbot and Charles Percy, Cuthbert Tunstall, the Bishop of London, and Sir Thomas Boleyn.
There is no need for spoilers beyond this point because we all know how this turned out. Henry VIII didn’t want to pay the full dowry after he felt betrayed by Charles V during their joint enterprise against France, and Charles V used this excuse to break the marriage treaty and marry his other first cousin, someone whom he didn’t have to wait for her to grow up because they were almost the same age, the Portuguese Infanta, Isabel of House Avis.
We do not know how Mary felt. Given that she was a child at the time the marriage broke, and her father felt betrayed yet again by her maternal family, she probably didn’t brood too much of it (if she did at all) and instead focused on her studies. Her mother would have been another case entirely as Katharine would have wanted both nations to be tied together against what she perceived to be their natural enemy, France. Had things gone differently, Mary’s situation would have been like Matilda, although probably less bellicose. As it happened, Mary would go on to be betrothed to countless more kings and princes and then when she was a bastard, minor royals in an effort to cement an alliance, but due to her gender, her lineage and her religious affiliation nothing would come out of it.
In the meantime, both parties were happy celebrating their alliance and the future marriage between Charles and Mary. Just as his daughter had previously showed off her artistic talents to their Spanish guests, Henry VIII did the same when he wrote to Charles an elaborate letter where he expressed deep gratitude for his arrival, and the amicability he’d showed to his ministers, including Cardinal Wolsey.
Sources:
- Porter, Linda. The Myth of Bloody Mary. St. Martin Press. 2008.
- Whitelock, Anna. Mary Tudor: Princess, Bastard, Queen. Random House. 2010.
- Williams, Patrick. Katharine of Aragon: The Tragic Story of Henry VIII’s First Unfortunate Wife. Amberley. 2013.
- Fox, Julia. Sister Queens: The Noble Tragic Lives of Katherine of Aragon and Juana, Queen of Castile. Ballantine Books. 2012.
- Weir, Alison. Henry VIII: The King and his Court. Ballantine Books. 2001.