Sir Fortescus was an English jurist and political theorist in the 15th century. He was the first to study the types of monarchy in England at the end of the middle Century and the differences between them and other monarchies. His special experience made him propose for the first time that Britain is "political and royal rule" to distinguish it from France's "royal rule". The above two types of feudal monarchies are very different in the formation process and the way of ruling, and the results of the ruling are also distinct. The pros and cons of the two are quite different. His theory of "politics and royal rule" not only reveals the type of British feudal monarchy at the end of the Middle Ages, but also has a foundational significance for the development of constitutional theory.