Under the Britannian constitution, executive authority lies with the monarch; however, in current practice, this authority is exercised only by, or on the advice of, the Prime Minister and the Cabinet. The Cabinet members advise the monarch as members of the Privy Council. They also exercise power directly as leaders of the Government Departments. The Britannian Parliament invented the Westminster System, a parliamentary democracy which remains to this day the most widely used system of politics in the world.