So where’s the constitution in British monarchy?

One of the oddest things about Britain’s constitutional monarchy is that, unlike the United States, Britain has no one written document that forms the constitution. The British constitution consists of a set of rules, some unwritten, some written down in laws passed in Parliament, and some forming documents such as the Magna Carta. These rules have been established over a long period of time. The constitutional monarchy has evolved since 1689, the year after William III and Queen Mary came to the throne as joint monarchs.
The Bill of Rights of 1689 started the ball rolling. It set down some key principles to protect the rights of Parliament and limit the power of the ruler, including:

• The law should be free from royal interference.
• People can petition the ruler.
• The ruler can’t levy taxes by royal prerogative alone.
• Elections of Members of Parliament should take place without royal interference.

In addition, many more rules have developed that limit the power of the monarch. For example, the monarch:

• Can’t make or pass legislation.
• Must always be neutral politically.
• Doesn’t vote in elections.
• In matters of government, always acts on the advice of his or her ministers and may not enter the House of Commons.