The Parliament of England was the legislature of the Kingdom of England. Its roots can be traced back to the early medieval period. In a series of developments, it came increasingly to constrain the power of the monarch, and went on after the Act of Union 1707 to form the main basis of the Parliament of Great Britain, and later the Parliament of the United Kingdom. This makes the modern Parliament of the United Kingdom one of the oldest legislative bodies in the world, arguably the oldest, and for this reason it is sometimes referred to as the "Mother of all Parliaments".