 The appointment of the prime minister is also , theoretically , governed by the royal prerogative . Technically the monarch may appoint as prime minister anyone she wants to appoint , but in practice the appointee is always the person who commands a majority in the House of Commons . Usually , this is the leader of the political party that is returned to Parliament with a majority of seats after a general election . <unk> may result with a so @-@ called hung parliament , in which no party commands majority support , as last occurred in 2010 . In this situation , constitutional convention is that the previous incumbent has the first right to form a coalition government and seek appointment . If the prime minister decides to retire in the middle of a parliamentary session , as Anthony Eden did in 1957 , the monarch has no discretion . There is usually a " prime minister @-@ in @-@ waiting " who commands the support of the majority of the Commons ; he or she will near @-@ automatically be appointed . 
