2016 United Kingdom European Union membership referendum in the context of "Dominic Cummings"

Article 50 of the Treaty on European Union (TEU) provides for the possibility of an EU member state leaving the European Union "in accordance with its own constitutional requirements".

Currently, the United Kingdom is the only state to have withdrawn from membership of the European Union. The process to do so began when the UK Government triggered Article 50 to begin the UK's withdrawal from the EU on 29 March 2017 following a June 2016 referendum, and the withdrawal was scheduled in law to occur on 29 March 2019. Subsequently, the UK sought, and was granted, a number of Article 50 extensions until 31 January 2020. On 23 January 2020, the withdrawal agreement was ratified by the Parliament of the United Kingdom, and on 29 January 2020 by the European Parliament. The UK left the EU on 31 January 2020 at 23:00 GMT, ending 47 years of membership.

David William Donald Cameron, Baron Cameron of Chipping Norton (born 9 October 1966), is a British politician who served as Prime Minister of the United Kingdom from 2010 to 2016. Until 2015, he led the first coalition government in the UK since 1945 and resigned after a referendum supported the country's leaving the European Union. After his premiership, he served as Foreign Secretary in the government of prime minister Rishi Sunak from 2023 to 2024. Cameron was Leader of the Conservative Party from 2005 to 2016 and served as Leader of the Opposition from 2005 to 2010. He was Member of Parliament (MP) for Witney from 2001 to 2016, and has been a member of the House of Lords since November 2023. Cameron identifies as a one-nation conservative and has been associated with both economically liberal and socially liberal policies.

Born in London to an upper-middle-class family, Cameron was educated at Eton College and Brasenose College, Oxford. After becoming an MP in 2001, he served in the opposition Shadow Cabinet under Conservative leader Michael Howard, and succeeded Howard in 2005. Following the 2010 general election, negotiations led to Cameron becoming prime minister as the head of a coalition government with the Liberal Democrats.

Theresa Mary May, Baroness May of Maidenhead (/təˈriːzə/; née Brasier; born 1 October 1956), is a British politician who served as Prime Minister of the United Kingdom and Leader of the Conservative Party from 2016 to 2019. She previously served as Home Secretary from 2010 to 2016. She was Member of Parliament (MP) for Maidenhead from 1997 to 2024, and has been a member of the House of Lords since August 2024. May was the second female British prime minister, after Margaret Thatcher, and the first woman to have held two of the Great Offices of State. May is a one-nation conservative.

May grew up in Oxfordshire and attended St Hugh's College, Oxford. After graduating in 1977, she worked at the Bank of England and the Association for Payment Clearing Services. She also served as a councillor on Merton London Borough Council. After two unsuccessful attempts to be elected to the House of Commons, she was elected MP for Maidenhead at the 1997 general election. From 1999 to 2010, May held several roles in shadow cabinets and was Chairman of the Conservative Party from 2002 to 2003. Following the formation of the coalition government after the 2010 general election, May was appointed home secretary and minister for women and equalities, giving up the latter role in 2012. Reappointed after the Conservatives won the 2015 general election, she became the longest-serving home secretary in more than 60 years. During her tenure as home secretary, she pursued reform of the Police Federation, implemented a harder line on drugs policy and further restricted immigration. She oversaw the introduction of elected police and crime commissioners, the deportation of Abu Qatada and the creation of the College of Policing and the National Crime Agency. Although she supported the Remain campaign, May supported Brexit following the outcome of the 2016 referendum. She was elected and appointed prime minister unopposed, succeeding David Cameron.

The European Union (Notification of Withdrawal) Act 2017 (c. 9) was an Act of the Parliament of the United Kingdom to empower the Prime Minister to give to the Council of the European Union the formal notice – required by Article 50 of the Treaty on European Union – for starting negotiations for the United Kingdom's withdrawal from the European Union. It was passed following the result of the 2016 United Kingdom European Union membership referendum held on 23 June in which 51.9% of voters voted to leave the European Union.

This is a list of referendums related to the European Union, or referendums related to the European Communities, which were predecessors of the European Union. Since 1972, a total of 48 referendums have been held by EU member states, candidate states, and their territories, with several additional referendums held in countries outside the EU. The referendums have been held most commonly on the subject of whether to become a member of European Union as part of the accession process, although the EU does not require any candidate country to hold a referendum to approve membership or as part of treaty ratification. Other EU-related referendums have been held on the adoption of the euro and on participation in other EU-related policies.

The United Kingdom is the only country as an EU member state to have held referendums on continued membership of the European Union and its antecedent organisation, the European Communities. In the first referendum in 1975, continued membership of what was then the European Communities (which included the European Economic Community, often referred to as the Common Market in the UK) was approved by 67.2% of voters, while in its second referendum in 2016 voters voted by 51.9% to leave the European Union, effectively reversing the result of the first referendum.

On 29 March 2017, the United Kingdom (UK) invoked Article 50 of the Treaty on European Union which began the member state's withdrawal, commonly known as Brexit, from the European Union (EU). In compliance with the treaty, the UK gave formal notice to the European Council of its intention to withdraw from the EU to allow withdrawal negotiations to begin.

The process of leaving the EU was begun after a referendum held in June 2016 at which 52% of the votes were in favour of UK withdrawal. In October 2016, the UK prime minister, Theresa May, announced that Article 50 would be invoked by "the first quarter of 2017". On 24 January 2017 the Supreme Court ruled in Miller I that the process could not be initiated without an authorising Act of Parliament, and unanimously ruled against the Scottish Government's claim in respect of devolution. Consequently, the European Union (Notification of Withdrawal) Act 2017 empowering the prime minister to invoke Article 50 was enacted in March 2017.

David Cameron's tenure as Prime Minister of the United Kingdom began on 11 May 2010 when he accepted an invitation of Queen Elizabeth II to form a government, succeeding Gordon Brown of the Labour Party, and ended on 13 July 2016 upon his resignation following the 2016 referendum that favoured Brexit, which he had opposed. As prime minister, Cameron also served simultaneously as First Lord of the Treasury, Minister for the Civil Service, and Leader of the Conservative Party.

Following the 2010 general election, Cameron became prime minister at the head of a coalition government between the Conservatives and Liberal Democrats, as no party had gained an overall majority in the House of Commons for the first time since the February 1974 general election. He appointed Nick Clegg, Leader of the Liberal Democrats, Deputy Prime Minister. Between them, the Conservatives and Liberal Democrats controlled 363 seats in the House of Commons, with a majority of 76 seats.

The 2015 United Kingdom general election was held on Thursday, 7 May 2015 to elect 650 members of Parliament (MPs) to the House of Commons. The Conservative Party, led by Prime Minister David Cameron, won an unexpected majority victory of ten seats; they had been leading a coalition government with the Liberal Democrats. It was the last general election to be held before the UK voted to leave the European Union (EU) in June 2016.

Opinion polls and political commentators had widely predicted that the election would result in a second consecutive hung parliament whose composition would be similar to the one elected at the previous general election in 2010. Potential coalitions and agreements between parties were intensively discussed; as a result, smaller parties received much more attention during the campaign than in previous UK elections. However, opinion polls underestimated the Conservatives, as they won 330 of the 650 seats and 36.9 per cent of the vote, giving them a small overall majority.

Britain Stronger in Europe (formally The In Campaign Limited) was an advocacy group which campaigned in favour of the United Kingdom's continued membership of the European Union in the 2016 British referendum. It was launched at the Old Truman Brewery in London on 12 October 2015, and declared as the official "Remain" campaign for the referendum by the Electoral Commission on 13 April 2016.

In the 2016 United Kingdom European Union membership referendum, 51.9% voted in favour of leaving the EU, which meant that the Britain Stronger in Europe campaign was unsuccessful in achieving its main goal.