The United Kingdom is a constitutional monarchy. A monarch is a hereditary ruler; a constitutional monarchy is a state headed by a monarch who rules according to the constitution.

The constitution may be unwritten, as it is in the United Kingdom, or codified as it is in almost all other monarchies.

In a constitutional monarchy, the sovereign reigns but does not rule.

Almost all of the Queen's constitutional powers are exercised on the 'advice' of her government. The advice she receives cannot be ignored: in practice, it is the Queen's ministers who make almost all the decisions.

Sovereignty resides not in the sovereign but with 'the Queen in parliament'. That means proposals need the approval of the Queen as well as the House of Commons and the House of Lords in order to become law.

In practice, however, parliament is supreme. Once a bill has been passed by both houses of parliament, the royal assent is always signified.

The monarchy could not survive any attempt to block legislation. The last monarch to use her veto was Queen Anne, in 1707.

The Queen is Supreme Governor of the Church of England and Head of the Commonwealth. These positions have symbolic importance. However, it would be wrong to imagine that the monarch is little more than a figurehead.

The Sovereign has important powers, and may still be called upon to exercise them. Under the British constitution, the monarch: