First of all, it's very important to point out that COMMON LAW based it's judicial decisions on precedent, this means that rulings were based on previous rulings made by other judges. This system has existed since the Middle Ages, and it has spread to countries like The United States of America, for example.
Trial by jury and applying the law equally throughout the land were also two other fundamental principles of Common Law. Juries were formed by people with no legal knowledge and without biased assumptions in order to make the final decision as unbiased as possible. Regarding equality, there was a principle also called "principle of equality" that established that every man and woman were equal under the eyes of the law, also making sure that the law was equally and impartially applied throughout the English land.
The only principle that is not part of the Common Law is establishing England as a Constitutional Monarchy.
England was established as a Constitutional Monarchy after the Glorious Revolution of 1688, limiting the power of the reigning monarch. Nowadays, the monarch is politically neutral and mostly has a ceremonial role.
