Henry Tudor agreed to the plan

To strengthen his claim and unite the two feuding noble houses, Elizabeth Woodville and Margaret Beaufort agreed that the latter's son should marry the former's eldest daughter, Elizabeth of York, who upon the death of her brothers became the heiress of the House of York. Henry Tudor agreed to this plan and in December 1483 publicly swore an oath to that effect in the cathedral in Rennes, France. A month earlier, an uprising in his favour, led by Buckingham, had been crushed.