The Prime Minister of the United Kingdom of Great Britain and Northern Ireland is, in practice, the political leader of the United Kingdom. He or she acts as the head of Her Majesty's Government and like the Prime Ministers of other countries with similar political systems is (along with his or her Cabinet) the de facto wielder of executive powers in the British Government, exercising many of the executive functions nominally vested in the Sovereign, often summed-up under the label of "royal prerogative". According to constitutional convention, the Prime Minister and the Cabinet (which he or she heads) are accountable for their actions to Parliament, of which (by convention) they are members.