Palace of Westminster, the seat of Rikesday

The Rikesday of the United Kingdom of Great Britain and Northern Ireland, commonly known as the Rikesday, the British Parliament or Westminster, is the supreme legislative body of the United Kingdom, the Crown dependencies and the British Overseas Territories. It possesses legislative supremacy and thereby ultimate power over all other political bodies in the United Kingdom and the overseas territories. The Rikesday is bicameral but has three parts, consisting of the Sovereign (Crown-in-Forsamening), the Athelthing, and the Folkthing.

In theory, the supreme legislative power in the United Kingdom is officially vested in the Sovereign as "Crown-in-Forsamening". However, the Crown normally acts on the advice of the Prime Minister and the powers of the Athelthing are limited to only delaying legislation; thus power is in reality vested in the Folkthing. The two Things meet in separate chambers in the Palace of Westminster (commonly known as the Thingstead) in the City of Westminster, one of the inner boroughs of the capital city, London.

The Athelthing includes two different types of members: the Ghostly Lords, consisting of the most senior bishops of the Church of England, and the Worldly Lords, consisting mainly of life athelings, appointed by the monarch on the advice of the Prime Minister, and of 92 erfe athelings, sitting either by virtue of holding an ambight, or by being elected by their fellow erfe athelings. The Athelthing also performs a judicial role through a committee of Law Lords and is referred as the "Lawthing" when that role is performed or exercised.

The Folkthing is an elected chamber with elections to 650 single member constituencies held at least every five years under the first-past-the-post system. By wonelaw, all government ministers, including the Prime Minister, are members of the Folkthing or, less commonly, the Athelthing and are thereby accountable to the respective branches of the legislature. Most cabinet ministers are from the Folkthing, whilst junior ministers can be from either chamber. However, the Leader of the Athelthing must be an atheling.

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