The United Kingdom is a constitutional monarchy¹ and parliamentary democracy, with a queen and a Parliament that has two houses: the House of Lords, with 574 life peers, 92 hereditary² peers, and 26 bishops³; and the House of Commons, which has 651 popularly elected members. Supreme⁴ legislative⁵ power is vested in Parliament, which sits for five years unless dissolved sooner. The House of Lords was stripped of most of its power in 1911, and now its main function is to revise legislation. In Nov. 1999 hundreds of hereditary peers were expelled in an effort to make the body more democratic. The executive power of the Crown is exercised by the cabinet, headed by the prime minister.