constitution

   The constitution is at the heart of most political systems, describing the fundamental rules by which a nation state or body politic is constituted and governed. Usually these rules are contained in a single written document, although in rare examples they may be located in major pronouncements, writings, statutes, precedents and legal decisions. Such constitutions may be an imperfect and incomplete guide to what actually happens in any country, but they help to shape the way in which systems of government function and give legitimacy to those who rule.

   Constitutions declare the existence of the state and express the most important principles, rules and procedures of the political system. They establish the formal structure of the state, specifying the powers and institutions of central government and its relationship with other tiers of administration. In addition, they usually outline the liberties and rights of citizens and in so doing create restrictions on and obligations of the government.

   The British constitution is almost unique, on account of its age, gradual evolution and uncodified status. Its major features are that it is not written down in a single document: it is flexible and therefore easy to amend and its commitment to the ideas of parliamentary sovereignty, the rule of law and the unitary state. Its main sources include major constitutional pronouncements (for example, Magna Carta), authoritative commentaries (for example, Erskine May), the royal prerogative, statutes, common law, conventions of the constitution and community law.