The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, [m] is a country located in northwestern Europe, off the coast of the continental mainland. It consists of England, Scotland, Wales, and Northern Ireland. It covers an area of ​​94,354 square miles (244,376 km2). Otherwise, the United Kingdom is surrounded by the Atlantic Ocean, the North Sea, the English Channel, the Celtic Sea, and the Irish Sea. The estimated population of the United Kingdom in 2023 was over 68.2 million. The capital and largest city of both England and the United Kingdom is London, whose wider metropolitan area is the largest in Western Europe, with a population of 14.9 million. The cities of Edinburgh, Cardiff, and Belfast are the national capitals of Scotland, Wales, and Northern Ireland, respectively. The lands of Britain have been continuously inhabited since the Neolithic period. In AD 43, the Roman conquest of Britain began; The Anglo-Saxon settlement followed the Roman departure. In 1066, the Normans conquered England. With the end of the Wars of the Roses, the English kingdom stabilized and began to grow in power, leading to the annexation of Wales, the Dominion of Scotland, and the establishment of the British Empire in the 16th century. During the 17th century, the role of the British monarchy declined, particularly as a result of the English Civil War. In 1707, the Kingdom of England and the Kingdom of Scotland united under the Treaty of Union to create the Kingdom of Great Britain. The Act of Union 1800 incorporated the Kingdom of Ireland in 1801 to form the United Kingdom of Great Britain and Ireland. Most of Ireland seceded from the UK in 1922 as the Irish Free State, and the Royal and Parliamentary Titles Act 1927 created the current United Kingdom.