He spent thirteen years performing a loyalty he had already decided to destroy. On the morning he betrayed it he was waiting for the right moment. He knew what the moment would look like. He had been waiting for it since 1472.
History remembers Margaret Beaufort as a devoted mother, a pious noblewoman, a woman who prayed for her son from a distance and wept when he finally came home. That is the story she wanted told. She was also the most dangerous political mind of the fifteenth century, and the two things are not separate.