It guarantees specified rights to nationals, establishes duties, the level of powers and important political principles of each government.
With constitutions from many countries from the common wealth being written, British constitutions has never been written down. What the Britons have as their constitution is a combination of statute law, convention and common law.
The 1982 Reform Act which was responsible for the parliamentary representation reforms, Magna Carta (1215) protecting the community rights against the crown and the Bill of Rights (1689) that made it impracticable for the sovereign to ignore the government wishes by extending the powers of the parliament.
Though it has never been well defined, common law is presumed to come from legal precedents or customs and interpreted in court cases by the judges. Practices and rules which are not legally enforceable are called conventions but regarded as crucial to the smooth working of the government. It is from the historical events through which the British system of government has originated that conventions are extracted. ...