although upland and mountainous terrain lies within the Southern Uplands. Wales accounts for less than one-tenth (9 per cent) of the total area of the UK, covering . Wales is mostly mountainous, though South Wales is less mountainous than North and mid Wales. The main population and industrial areas are in South Wales, consisting of the coastal cities of Cardiff, Swansea and Newport, and the South Wales Valleys to their north. The highest mountains in Wales are in Snowdonia and include Snowdon () which, at , is the highest peak in Wales. Wales has over of coastline. Several islands lie off the Welsh mainland, the largest of which is Anglesey (Ynys Môn) in the north-west. Northern Ireland, separated from Great Britain by the Irish Sea and North Channel, has an area of and is mostly hilly. It includes Lough Neagh which, at , is the largest lake in the British Isles by area. The highest peak in Northern Ireland is Slieve Donard in the Mourne Mountains at . Government and politics Constitutional principles The Constitution of the United Kingdom is uncodified and consists mostly of a collection of disparate written sources, including statutes, judge-made case law and international treaties, together with constitutional conventions. Nevertheless, the Supreme Court recognises a number of principles underlying the British constitution, such as parliamentary sovereignty, the rule of law, democracy, and upholding international law. The Supreme Court also recognises that some acts of Parliament have special constitutional status, and are therefore part of the constitution. These include Magna Carta, which in 1215 required the King to call a "common counsel" (now called Parliament) to represent people, to hold courts in a fixed place, to guarantee fair trials, to guarantee free movement of people, to free the church from the state, and to guarantee rights of "common" people to use the land. (Most of Magna Carta is no longer in force; those principles it established that still exist are mostly protected by other enactments.) After the Wars of the Three Kingdoms and the Glorious Revolution, the Bill of Rights 1689 and the Claim of Right Act 1689 cemented Parliament's position as the supreme law-making body, and said that the "election of members of Parliament ought to be free". In accordance with the principle of parliamentary sovereignty, the UK Parliament can carry out constitutional reform through acts of Parliament, and thus has the political power to change