Britain’s scheduled departure from the EU is less than three months away.
Here are some of the key milestones witnessed on the road to Brexit day:
June 23, 2016
The UK votes for Brexit in the EU referendum by 51.9% to 48.1%, prompting the then-prime minister David Cameron to resign and be replaced by Theresa May.
January 17, 2017
Mrs May gives a speech at Lancaster House setting out the Government’s 12-point "Plan for Britain" and her negotiating red lines, ruling out membership of the EU’s single market and customs union.
March 29, 2017
The PM triggers Article 50 of the Lisbon Treaty, which formally kick-starts a two-year countdown to the UK exiting the EU.
June 8, 2017
After calling a snap general election to increase her authority, the PM loses her parliamentary majority and has to make a deal with the DUP to stay in power.
December 13, 2017
Rebel Tory MPs inflict a major defeat on the Government, forcing them to guarantee the Commons a vote on the final Brexit deal.
December 15, 2017
Two days later the first part of the negotiations is completed after a deal is reached on the "divorce bill", and the so-called Northern Irish "backstop" is first agreed upon.
March 2, 2018
Mrs May gives her second big Brexit speech, this time at Mansion House, outlining her "five tests" for the UK’s future economic partnership with the EU.
March 19, 2018
A draft Withdrawal Agreement is published, which Michel Barnier and David Davis call a "decisive step" in the Brexit process, setting out the transition period, citizens’ rights and plans for fishing.
July 6, 2018
After the The European Union (Withdrawal) Bill becomes law at the end of June, Mrs May takes her Cabinet to Chequers to sign off a collective position for the future Brexit negotiations with the EU.
July 9, 2018
Brexit Secretary David Davis resigns over the so-called "Chequers Plan" to be replaced by Dominic Raab, with Foreign Secretary Boris Johnson following him out of Cabinet several days later.
September 20, 2018
November 25, 2018
A 599-page draft Withdrawal Agreement is published after unanimous approval by the EU, but the terms of the backstop to prevent a hard border in Ireland spark anger among Brexiteers and the DUP.
December 10, 2018
Mid-way through a five-day debate on the Brexit deal, as it became clear she would lose heavily, Mrs May pulls the vote and postpones it until the week of January 14, 2019.
December 12, 2018
In response, enough discontented Tory MPs write letters of no confidence to reach the threshold for a vote in her leadership, which she wins by 200 to 117 the following day.
December 19, 2018
The European Commission starts implementing its "no deal" Contingency Action Plan, covering 14 areas where UK withdrawal without a deal would create "major disruption for citizens and businesses" in the remaining 27 EU states.
January 9, 2019
After returning from the Christmas break, MPs begin five days of debate on the PM’s deal.
January 14, 2019
Mr Tusk and European Commission president Jean-Claude Juncker release a letter offering "clarifications" to the withdrawal agreement.
What happens next?
Theresa May's Brexit deal was overwhelmingly defeated in Parliament on Tuesday evening by a majority of 230.
Reacting to the result, Mrs May said: "The House has spoken and the Government will listen."
Jeremy Corbyn described the defeat as "catastrophic", and said that Labour would table a vote of no-confidence in the government, which would be discussed in parliament on Wednesday.