The Prime Minister and Cabinet are formally appointed by the Monarch to form Her Majesty's Government, though the Prime Minister chooses the Cabinet, and by convention HM The Queen respects the Prime Minister's choices.
It is governed by a parliamentary system with its seat of government in London, the capital, but with three devolved national administrations in Belfast, Cardiff and Edinburgh, the capitals of Northern Ireland, Wales and Scotland respectively. but the economic and social cost of two world wars and the decline of its empire in the latter half of the 20th century diminished its leading role in global affairs.
The UK nevertheless remains a major power with strong economic, cultural, military, scientific and political influence.
The UK has a parliamentary government based on the Westminster system that has been emulated around the world—a legacy of the British Empire.
The Parliament of the United Kingdom that meets in the Palace of Westminster has two houses: an elected House of Commons and an appointed House of Lords, and any Bill passed requires Royal Assent to become law.
The Crown has sovereignty over the Crown Dependencies of the Isle of Man and the Bailiwicks of Jersey and Guernsey, which are not part of the United Kingdom though the UK government manages their foreign affairs and defence and the UK Parliament has the authority to legislate on their behalf.