The head of the British Government is the Prime Minister. The leader of the largest party in the House of Commons is by convention asked by the monarch to be Prime Minister and to form a government. This can only take place after the loser of the election has conceded defeat and tendered his or her resignation in person at the Palace.
In the event that there is no clear winner - a hung Parliament - the 'sitting' Prime Minister is permitted to remain in office until it is necessary to resign, whether that be as a result of failed coalition negotiations or after the Government's legislative programme (the Queen's Speech) is defeated in the Commons, in which case the Leader of the Opposition would be invited to form a government.
The guiding principles for the use of the monarch's 'personal prerogative' are that government should persist and that there should not be elections in quick succession. The monarch's Private Secretary meets with the Cabinet Secretary to consider what options are available, but the ultimate decision remains with the Crown.
Once appointed by the monarch (in the ceremony known anachronistically as the 'kissing of the hands'), the Prime Minister has absolute discretion over who will be invited to become Ministers, what direction the Government and country will take and how the departments of government will be structured.
The holder of the office has ultimate power over, and responsibility for, all policies made and implemented by government, seeing all Cabinet papers and being the sole arbiter of disputes between the organs of government.
Added to these over-arching responsibilities are individual powers to operate the Royal Prerogative (as the de facto chair of the Privy Council) - to declare war (including single-handedly authorising the launch of a nuclear strike), to sign international treaties and to represent the UK at the highest level in international and European negotiations.
It is the Prime Minister alone who requests the dissolution of Parliament, triggering a general election, and who has overall responsibility for the use of Government time in the House of Commons and the House of Lords. The Prime Minister's accountability to Parliament comes in the form of oral questions once a week and scrutiny at the hands of the Commons' Liaison Committee every six months.
Other Prime Ministerial powers include those to recommend the appointment of key figures, including peers, religious leaders, top judges and military heads as well as the chairs of public corporations such as the BBC.
Prime Ministers have a weekly audience with the monarch, normally on a Tuesday evening. It is widely held that this traditional meeting of the heads of government and state provides the Prime Minister with the chance to reflect on events, to consult and seek advice on affairs of state with the absolute knowledge of confidentiality.
The title 'Prime Minister' is somewhat amorphous and hardly appears on the statute book, even then it is referred to as a 'position' rather than an 'office'. The Prime Minister has the title of First Lord of the Treasury (the name on the door of 10 Downing Street) and Minister for the Civil Service. By convention, the Prime Minister is said to be 'primus inter pares' (first among equals) in Cabinet.