The politics of the United Kingdom take the shape of a parliamentary democracy presided over by the Prime Minister. It is a multi-party system where Executive power is wielded by the ruling party (the government), whereas legislative power is exercised by a combination of the Upper and Lower houses (Lords and Commons).
The Commons itself is made up of constituency MPs representing the whole country and the government of the day is both drawn from and is answerable to its members.
A constant factor in British governance is the presence of civil servants behind the scenes who retain their positions even when there is a change of government. Many of the countries that make up the Commonwealth - such as Australia, New Zealand and India - have emulated the British parliamentary system, which is known as 'The Westminster System'.
The UK has a nominal head of state, the monarch, but their powers are said to be ceremonial and it is the presiding government that holds sovereignty, making decisions by the monarch's leave rather than because of their orders.
The monarch must appoint a new Prime Minister (although, in practice, this simply means the leader of the party with the most seats) who then selects those he wants for Cabinet Ministers to form the government.
Made up of around a hundred ministers, the government comprises a number of departments such as The Home Office or The Ministry of Defence headed by a Secretary of State.
Also see the City of London section and the Monarchy section.