What is the theme in The Constant Princess by Philippa Gregory?

The quest for power is a major theme in the story. Catalina has been raised from infancy to know that she is Princess of Wales and future Queen of England. The fact that she was the beloved Infanta of Spain is simply a forerunner of the great woman she is destined to be. She believes completely in that destiny. When the time comes to travel to England, she does so though she admits that she misses her mother. She often says that she is just a girl and that she still needs her mother, but that she is doing what she was supposed to do for her coming role as queen. She seems to have believed that enduring the trip to England and being away from her mother were hardships, but they were nothing compared to the hardships she was to endure over the coming years.