Brexit timeline - 'The clock is ticking'

24 June 2016 – Prime minister David Cameron announces his resignation.

13 July 2016 – Theresa May becomes UK prime minister.

27 July 2016 – EU Commission president Jean-Claude Juncker appoints Michel Barnier as the EU's chief Brexit negotiator.

8 September 2016 – The European Parliament, which needs to back the divorce agreement, appoints liberal MEP Guy Verhofstadt as its top Brexit representative.

3 January 2017 – Sir Ivan Rogers, the UK ambassador to the EU, resigns. In a letter to his staff, he warns of the dangers of "muddled thinking" in London.

4 January 2017 – Sir Tim Barrow, a career diplomat and former ambassador to Russia, is appointed as the UK's new ambassador to the EU.

17 January 2017 – Prime minister Theresa May gives her Lancaster House speech in which she sets out her government's priorities in the Brexit negotiations, including specifically leaving the EU's single market and customs union.

24 January 2017 – The UK's Supreme Court rejects the government's appeal in the Gina Miller case, ruling that the parliament must vote on whether Article 50 exit procedures can be triggered.

2 February 2017 – The UK government publishes its Brexit White Paper, setting out its strategy for exiting the EU.

13 March 2017 – The UK parliament passes the European Union (Notification of Withdrawal) Bill, later confirmed by the Queen's 'Royal Assent', giving the green light to trigger Article 50.

29 March 2017 – Prime minister Theresa May sends a letter to European Council president Donald Tusk to notify him of the UK's intent to leave the EU, formally triggering Article 50.

31 March 2017 – European Council chief Donald Tusk publishes draft negotiation guidelines for Brexit talks for the EU-27, setting out the key issues - encompassing citizens' rights, the border between Northern Ireland and Ireland and the financial settlement – to be discussed in the first phase of talks. Tusk reiterates that future relations and trade discussions may only begin once the key issues are resolved.

29 April 2017 – EU-27 leaders unanimously endorse the draft guidelines for Brexit negotiations.

22 May 2017 – The EU-27 adopts the negotiating directives, giving the green light for negotiators to start discussions.

8 June 2017 – The UK holds snap general elections as Theresa May attempts to consolidate the power of her Conservatives. She miscalculates and loses the Tory majority in parliament, leaving her with a minority government backed by Northern Ireland's ultra- conservative Democratic Unionist Party (DUP).

19 June 2017 – Brexit negotiations begin with establishing the timeline for talks, and forming negotiating groups.

17-20 July 2017 – Second round of negotiations take place in Brussels. Both sides say they are committed to the Good Friday Agreement, which has secured peace and stability in Northern Ireland. Negotiators set out to compare positions on citizens' rights. Barnier urges the UK to clarify its position on the financial settlement and its plans to secure a frictionless border between Northern Ireland and Ireland.

28–31 August 2017 – During the third round of talks, further progress is made on citizens' rights, but the role of the European Court of Justice in enforcing them, and the extent of the UK's financial obligations still remain outstanding key issues.

9 September 2017 – The EU Commission publishes several negotiating papers, including on Northern Ireland, emphasising that it is the UK's responsibility to propose solutions for the post-Brexit Irish border.

22 September 2017 – Prime minster Theresa May makes a speech in Florence to clarify the UK's Brexit position. Against the backdrop of hardline Brexiteers in her party, she pledges that no EU country would have to pay more or receive less from the EU budget as the result of the UK leaving the bloc, and that the UK would honour commitments it has made as a member. She also proposes a two-year transition period.

25 September 2017 – The fourth round of talks are held in Brussels a week later than planned to give way for May's Florence speech. EU negotiators were hoping to see a detailed commitment following May's pledges in Florence, but the UK still did not disclose details about its financial obligations. The UK offered to transpose the withdrawal agreement into UK law and ensure the UK courts can refer directly to it, but there was no agreement on the future role of the European Court of Justice.

9-12 October 2017 – The fifth round of negotiations again makes no progress on the key issues. No further rounds of talks were scheduled at the time, leading Barnier to say that negotiations have reached a "deadlock."

16 October 2017 – EU Commission president Jean-Claude Juncker hosts prime minister Theresa May for dinner, ahead of a crucial EU summit. The two agree that Brexit talks should "accelerate over the months to come."

20 October 2017 – EU-27 leaders agree that no "sufficient progress" has been made in Brexit talks to be able to move discussions into the next phase on future relations, including trade. But to show good faith, the EU-27 agreed to start internal preparations for trade talks, so that the EU is ready when those talks begin.

9-10 November 2017 – A new negotiating round kicks off among growing concerns that the slow pace of negotiations might result in a possible no-deal scenario. EU leaders will assess the state of talks again at the summit set for 14-15 December summit.

4 December 2017 – British prime minister Theresa May travels to Brussels in the hope of finalising the deal on the terms of divorce with the EU, but last minute objections from her political allies, the Democratic Unionist Party (DUP) over the Irish border issue prevent the agreement.

8 December 2017 – A deal is reached on the key divorce issues between the EU and the UK after DUP has agreed to a compromise text on the Irish border issue. British prime minister Theresa May and EU Commission president Jean-Claude Juncker announce the deal in the early hours of the morning in Brussels.

15 December 2017 – EU leaders agree that "sufficient progress" has been achieved on the key divorce issues with the UK and adopt guidelines to start negotiations on a possible transition period after the UK leaves the EU in 2019.

30 March 2019 – The UK is officially out of the EU.

This timeline was originally published in EUobserver's 2017 Europe in Review Magazine.

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