The United Kingdom of Great Britain and Ireland, commonly known as the United Kingdom (UK) or simply Britain, is a sovereign state located off the north-western coast of continental Europe. The country includes the islands of Great Britain (a term sometimes also loosely applied to the whole state), Ireland, Heligoland and many smaller islands. the UK is surrounded by the Atlantic Ocean, with the North Sea in the east, the English Channel in the south and the Irish Sea in the west. The UK's form of government is a constitutional monarchy with a parliamentary system. Its capital city is London. The current British monarch—since 6 February 1952—is Queen Elizabeth II. The United Kingdom consists of four countries: England, Scotland, Wales and Ireland. The latter three have devolved administrations, each with varying powers, based in their capital cities, Edinburgh, Cardiff and Dublin, respectively. Guernsey, Jersey, Heligoland and the Isle of Man are British Crown dependencies and the British Government is responsible for defence and international representation. The United Kingdom has 15 British Overseas Territories. These are the remnants of the British Empire which, at its height in the late 19th and early 20th centuries, encompassed almost a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a developed country and has the world's sixth-largest economy by nominal GDP and eighth-largest by purchasing power parity. It was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a recognised nuclear weapons state and its military expenditure ranks from fourth to sixth (depending on the source) in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946. It has been a member of the Commonwealth of Nations, the G7, the G8, the G20, NATO, the Organisation for Economic Co-operation and Development (OECD) and the World Trade Organization (WTO).