The UK holds a referendum on whether to leave the European Union. 51.9% of voters vote to leave.

David Cameron announces his resignation as Prime Minister.

Theresa May accepts the Queen's invitation to form a government. David Davis is appointed the newly created Secretary of State for Exiting the European Union to oversee withdrawal negotiations.

The European Commission nominates French politician Michel Barnier as European Chief Negotiator for the United Kingdom Exiting the European Union.

The UK House of Commons votes 461 to 89 in favour of Theresa May's plan to trigger Article 50 by the end of March 2017.

The UK Supreme Court rules in the Miller case that Parliament must pass legislation to authorise the triggering of Article 50.

The UK Government introduces a 137-word bill in Parliament to empower Theresa May to initiate Brexit by triggering Article 50. Labour leader Jeremy Corbyn instructs his MPs to support it.

The bill receives Royal Assent.

A letter from Theresa May is handed to President of the European Council Donald Tusk to invoke Article 50, starting a two-year process with the UK due to leave the EU on 29 March 2019.

Theresa May announces that a general election is to take place on 8 June.

A general election is held in the UK. The Conservative Party remains the largest single party in the House of Commons but loses its majority, resulting in the formation of a minority government with a confidence-and-supply arrangement with the Democratic Unionist Party (DUP) of Northern Ireland.

Brexit negotiations commence.

A UK white paper on the future relationship between the UK and the EU, known as the Chequers agreement, is finalised.

Davis resigns as Secretary of State for Exiting the European Union. Dominic Raab is appointed as his successor the following day.

Boris Johnson resigns as Foreign Secretary.

The EU rejects the UK white paper.

The Brexit withdrawal agreement is published.

Raab resigns as Secretary of State for Exiting the European Union. Stephen Barclay is appointed as his successor the following day.

27 other EU member states endorse the Withdrawal Agreement.

The First meaningful vote is held on the Withdrawal Agreement in the UK House of Commons. The UK Government is defeated by 432 votes to 202.

Second meaningful vote on the Withdrawal Agreement with the UK Government defeated again by 391 votes to 242.

UK Government motion passes 412 to 202 to extend the Article 50 period.

Theresa May requests the EU extend the Article 50 period until 30 June 2019.

The European Council offers to extend the Article 50 period until 22 May 2019 if the Withdrawal Agreement is passed by 29 March 2019 but, if it does not, then the UK has until 12 April 2019 to indicate a way forward. The extension is formally agreed the following day.

The original end of the Article 50 period and the original planned date for Brexit. Third vote on the Withdrawal Agreement after being separated from the Political Declaration. UK Government defeated again by 344 votes to 286.

Theresa May requests for a second time that the EU extend the Article 50 period until 30 June 2019.

The European Council grants another extension to the Article 50 period to 31 October 2019, or the first day of the month after that in which the Withdrawal Agreement is passed, whichever comes first. However, the UK must hold European Parliament elections in May 2019 (it did); otherwise it will leave on 1 June 2019.

Theresa May announces that she will resign as Conservative Party leader, effective 7 June, due to being unable to pass her Brexit plans through parliament and several votes of no-confidence,[153] continuing as prime minister while a Conservative leadership contest takes place.

MPs approve, with a majority of 41, an amendment to the Northern Ireland (Executive Formation etc) Act 2019 that blocks suspension of Parliament between 9 October and 18 December, unless a new Northern Ireland Executive is formed.

Boris Johnson accepted the Queen's invitation to form a government and became Prime Minister of the United Kingdom, the third since the referendum.

Both Houses of Parliament went into summer recess on 25 July until 3 September.

Boris Johnson announced his intention to end the current session of Parliament in September so the Queen would make a new speech on 14 October. This was controversial because it would limit the time for Parliament to act ahead of the Article 50 deadline of 31 October.[158] The Queen approved the timetable at a meeting of her Privy Council in Balmoral.[159]

 A motion for an emergency debate to pass a bill that would rule out a unilateral no-deal Brexit by forcing the Government to reach an Agreement, get parliamentary approval for no-deal Brexit. This motion, to allow the debate for the following day, passed, 328 to 301. 21 Conservative MPs voted for the motion.

The Benn Bill passed second reading by 329 to 300; a 22nd Conservative, Caroline Spelman, voted against the Government position. Later the same day MPs subsequently rejected Johnson's motion to call an October general election, failing to achieve the two-thirds Commons majority needed under the Fixed-term Parliaments Act, in a vote of 298 to 56. Labour MPs abstained from the vote.

 The Government again loses an attempt to call an election under the Fixed-term Parliaments Act. Dominic Grieve's humble address, requiring key Cabinet Office figures to publicise private messages about the prorogation of parliament, is passed by the House of Commons. Speaker John Bercow announces his intention to resign as Speaker of the House of Commons on or before 31 October. The Benn Bill receives Royal Assent and becomes the European Union (Withdrawal) (No. 2) Act 2019. Parliament is prorogued until 14 October 2019. Party conference season begins, with anticipation building around a general election.

The Supreme Court of the United Kingdom rules unanimously that Boris Johnson's decision to advise the Queen to prorogue parliament was unlawful, and that the prorogation itself is therefore null and of no effect.