On 23 June 2016, the United Kingdom voted to leave the European Union in a referendum. After the referendum, it was debated as to how and when the UK should leave the EU. On 11 July 2016, the Cabinet Office Minister, John Penrose failed to deliver a final answer on whether it would be at the disposal of the Prime Minister and one of the Secretaries of State, through the royal prerogative, or of Parliament, through primary legislation.