The British Parliament is composed of two houses. Commoners were first summoned to advise Edward I. As the concept of democracy grew, power gradually shifted from the hereditary House of Lords to the elected House of Commons.
Originally, representation in parliament was not directly linked to population. Among the great reforms of the 19th century was the abolition of "rotten boroughs" and the concept of population equality for all parliamentary ridings.
Unlike the system in the United States, both the executive and legislative branches of British government derive their power from the House of Commons. Any party with a majority of Member of Parliaments forms the government, their leader becoming Prime Minister. If no party has a majority, the largest party normally forms a government in a coalition with smaller parties. Cabinet ministers are always in Parliament. Formerly, they were often in the House of Lords. Like the House of Lords, the House of Commons meets in the Houses of Parliament at Westminster.