British Prime Minister Theresa May said Monday that she had secured legal guarantees from the European Union that should convince British lawmakers to back her Brexit deal.

The guarantees would ensure that the deal's most controversial provision, the so-called Irish backstop, would only apply temporarily after the UK leaves the EU on March 29.

"MPs were clear that legal changes were needed to the [Irish] backstop. Today we have secured legal changes," May told reporters at a joint press conference with EU Commission President Jean-Claude Juncker.

Read more: Brexit: Why is the Irish backstop so controversial?

What both sides agreed on:

May said both sides agreed on three documents — a "joint instrument," a joint statement and a unilateral declaration — that would accompany the main Brexit deal:

The legally binding "joint instrument" would allow the UK to challenge the EU in court if it tried to apply the backstop indefinitely and, if successful, suspend it.

The joint statement calls for an agreement on a post-Brexit trade deal before a transition period ends in December 2020. That would avoid the need to apply the backstop at all.

The UK would also make a unilateral declaration that the backstop would no longer apply if talks on a future trade deal collapse.

Read more: The draft Brexit deal — what you need to know

Brexit timeline: Charting Britain's turbulent exodus from Europe June 2016: 'The will of the British people' After a shrill referendum campaign, nearly 52% of British voters opted to leave the EU on June 23. Polls had shown a close race before the vote with a slight lead for those favoring remaining in the EU. Conservative British Prime Minister David Cameron, who had campaigned for Britain to stay, acknowledged the "will of the British people" and resigned the following morning.

Brexit timeline: Charting Britain's turbulent exodus from Europe July 2016: 'Brexit means Brexit' Former Home Secretary Theresa May replaced David Cameron as prime minister on July 11 and promised the country that "Brexit means Brexit." May had quietly supported the Remain campaign before the referendum. She did not initially say when her government would trigger Article 50 of the EU treaty to start the two-year talks leading to Britain's formal exit.

Brexit timeline: Charting Britain's turbulent exodus from Europe March 2017: 'We already miss you' May eventually signed a diplomatic letter over six months later on March 29, 2017 to trigger Article 50. Hours later, Britain's ambassador to the EU, Tim Barrow, handed the note to European Council President Donald Tusk. Britain's exit was officially set for March 29, 2019. Tusk ended his brief statement on the decision with: "We already miss you. Thank you and goodbye."

Brexit timeline: Charting Britain's turbulent exodus from Europe June 2017: And they're off! British Brexit Secretary David Davis and the EU's chief negotiator, Michel Barnier, kicked off talks in Brussels on June 19. The first round ended with Britain reluctantly agreeing to follow the EU's timeline for the rest of the negotiations. The timeline split talks into two phases. The first would settle the terms of Britain's exit, and the second the terms of the EU-UK relationship post-Brexit.

Brexit timeline: Charting Britain's turbulent exodus from Europe July-October 2017: Money, rights and Ireland The second round of talks in mid-July began with an unflattering photo of a seemingly unprepared British team. It and subsequent rounds ended with little progress on three phase one issues: How much Britain still needed to pay into the EU budget after it leaves, the post-Brexit rights of EU and British citizens and whether Britain could keep an open border between Ireland and Northern Ireland.

Brexit timeline: Charting Britain's turbulent exodus from Europe December 2017: Go-ahead for phase 2 Leaders of the remaining 27 EU members formally agreed that "sufficient progress" had been made to move on to phase two issues: the post-Brexit transition period and the future UK-EU trading relationship. While Prime Minister Theresa May expressed her delight at the decision, European Council President Tusk ominously warned that the second stage of talks would be "dramatically difficult."

Brexit timeline: Charting Britain's turbulent exodus from Europe July 2018: Johnson, Davis resign British ministers appeared to back a Brexit plan at May's Chequers residence on July 6. The proposal would have kept Britain in a "combined customs territory" with the EU and signed up to a "common rulebook" on all goods. That went too far for British Foreign Minister Boris Johnson and Brexit Secretary David Davis, who resigned a few days later. May replaced them with Jeremy Hunt and Dominic Raab.

Brexit timeline: Charting Britain's turbulent exodus from Europe September 2018: No cherries for Britain May's Chequers proposal did not go down well with EU leaders, who told her at a summit in Salzburg in late September that it was unacceptable. EU Council President Tusk trolled May on Instagram, captioning a picture of himself and May looking at cakes with the line: "A piece of cake perhaps? Sorry, no cherries." The gag echoed previous EU accusations of British cherry-picking.

Brexit timeline: Charting Britain's turbulent exodus from Europe November 2018: Breakthrough in Brussels EU leaders endorsed a 585-page draft divorce deal and political declaration on post-Brexit ties in late November. The draft had been widely condemned by pro- and anti-Brexit lawmakers in the British Parliament only weeks earlier. Brexit Secretary Dominic Raab resigned along with several other ministers, and dozens of Conservative Party members tried to trigger a no-confidence vote in May.

Brexit timeline: Charting Britain's turbulent exodus from Europe December 2018: May survives rebellion In the face of unrelenting opposition, May postponed a parliamentary vote on the deal on December 10. The next day, she met with German Chancellor Angela Merkel to seek reassurances that would, she hoped, be enough to convince skeptical lawmakers to back the deal. But while she was away, hard-line Conservative lawmakers triggered a no-confidence vote. May won the vote a day later.

Brexit timeline: Charting Britain's turbulent exodus from Europe January 2019: Agreement voted down The UK Parliament voted 432 to 202 against May's Brexit deal on January 16. In response to the result, European Council President Donald Tusk suggested the only solution was for the UK to stay in the EU. Meanwhile, Britain's Labour Party called for a no-confidence vote in the prime minister, her second leadership challenge in as many months.

Brexit timeline: Charting Britain's turbulent exodus from Europe March 2019: Second defeat for May's deal May tried to get legal changes to the deal's so-called Irish backstop in the weeks that followed. She eventually got assurances that the UK could suspend the backstop under certain circumstances. But on March 12, Parliament voted against the revised Brexit deal by 391 to 242. EU leaders warned the vote increased the likelihood of a no-deal Brexit. Two days later, MPs voted to delay Brexit.

Brexit timeline: Charting Britain's turbulent exodus from Europe March 2019: Extension after second defeat Following the second defeat of May's divorce deal, the European Council met in Brussels on March 21 to decide what to do next. EU leaders gave May two options: delay Brexit until May 22 if MPs vote for the withdrawal deal or delay it until April 12 if they vote against the deal. If the deal were to fail again in Parliament, May could ask for a long extension.

Brexit timeline: Charting Britain's turbulent exodus from Europe March 2019: Brexit deal rejected a third time On March 29, the day that the UK was supposed to leave the EU, British lawmakers voted for a third time against May's deal — rejecting it this time with a vote of 344 to 286. Following the latest defeat, May approached the main opposition Labour leader Jeremy Corbyn in an attempt to find a compromise, angering hardline Brexiteers in her own Conservative party.

Brexit timeline: Charting Britain's turbulent exodus from Europe April 2019: Brexit delayed until Halloween With the April 12 deadline looming after the third defeat of May's deal, EU leaders met again in Brussels to discuss a second delay. The only question was how long should it be? In the end, the UK and EU agreed to a "flexible" extension until October 31 — which can end sooner if the Brexit deal is approved. The UK had to take part in EU elections in May because their exit wasn't secured in time.

Brexit timeline: Charting Britain's turbulent exodus from Europe May 2019: Prime Minister Theresa May resigns Weeks of talks between Prime Minister Theresa May and the Labour party to reach a deal proved unsuccessful and further eroded her political capital. She triggered an angry backlash from her party after she tried to put the option of a second referendum on the table. The series of failures led May to announce her resignation, effective June 7, in an emotional address.

Brexit timeline: Charting Britain's turbulent exodus from Europe June 2019: Search for a new prime minister After Theresa May announced on June 7 that she would leave office, other members of her Conservative party began clamoring for the top job. Within a month, the leadership battle came down to Jeremy Hunt (left), an EU proponent who fears a no-deal scenario, and Boris Johnson (right), one of the main proponents of Brexit.

Brexit timeline: Charting Britain's turbulent exodus from Europe July 2019: Prime Minister Boris Johnson At the end of July 2019, Johnson was officially named Theresa May's successor as British prime minister. "We are going to energize the country, we are going to get Brexit done by October 31," he said after he was elected leader of the Conservative Party.

Brexit timeline: Charting Britain's turbulent exodus from Europe September 2019: Johnson's election threat Conservative rebels and opposition MPs backed efforts to delay an October 31 Brexit deadline in fear of a no-deal departure. In response, Johnson called for a general election, saying his government cannot rule without a mandate after he stripped 21 rebel MPs of their Conservative status. The Labour Party said it would not back elections until legislation to block a no-deal Brexit was in place.

Brexit timeline: Charting Britain's turbulent exodus from Europe September 2019: Prorogation 'unlawful' In late September, Britain's highest court ruled that Johnson's decision to suspend Parliament ahead of the UK's planned exit was unlawful. "This was not a normal prorogation in the run-up to a Queen's Speech," said the Supreme Court. Political rivals immediately called on Johnson to leave his post. Johnson said he would abide by the court ruling, though said he "strongly" disagreed.

Brexit timeline: Charting Britain's turbulent exodus from Europe October 2019: A new deal British Prime Minister Boris Johnson managed to secure a deal with European negotiators that would allow the UK to leave the EU in an orderly manner. The deal received unanimous backing from the leaders of 27 other member states. But an attempt to get the UK Parliament to sign off on the deal failed. Instead, Parliament pushed for the Brexit deadline to be extended until the end of January 2020.

Brexit timeline: Charting Britain's turbulent exodus from Europe December 2019: Lawmakers vote for Johnson's Withdrawal Bill On December 22, UK lawmakers vote for Prime Minister Johnson's European Union withdrawal bill, which will see a leave date of January 31 2020 enshrined in law. Getting a majority to vote to pass the bill in the lower house has proven a major sticking point for the PM, but following a general election Johnson's Conservative party won control of the house and the bill passed with a 124 majority.



What is the Irish backstop?

The backstop aims to keep an open border between Northern Ireland, a British territory, and the Republic of Ireland, an EU member, if both sides fail to agree on a post-Brexit trade deal.

But many pro-Brexit British lawmakers have rejected the entire Brexit deal because they fear that the backstop could force the UK to follow EU rules indefinitely if trade talks break down.

Why is this important?

The apparent breakthrough in talks between May and Juncker in Strasbourg came as British lawmakers prepared to vote for a second time on May's Brexit deal on Tuesday.

A large majority of lawmakers, which included many in May's Conservative Party, rejected the original Brexit deal in January. Key Remainers in May's Conservative Party have hinged their support to the attorney general's legal opinion on the latest backstop provisions.

Read more: Brexit: What Europe wants

Labour leader Jeremy Corbyn quickly rejected the new agreements as insufficient

Labour party rejects changes

The head of Labour, the UK's main opposition party, said the documents were insufficient and called on his colleagues to vote against the deal.

"The Prime Minister's negotiations have failed. Last night's agreement with the European Commission does not contain anything approaching the changes Theresa May promised parliament," Corbyn said on Twitter. "That’s why lawmakers must reject this deal today."

Read more:EU Customs Union, Single Market, Brexit — What you need to know

What happens if Parliament rejects the deal?

If the deal fails to secure a majority, lawmakers will vote on Wednesday on whether to rule out a no-deal Brexit. If that passes, they will then vote on extending the Brexit deadline during a parliamentary session on Thursday.

EU: This is your last chance

Sitting alongside May in Strasbourg, Juncker warned British lawmakers that the bloc would not reopen talks if they voted against May's deal.

"In politics, sometimes you get a second chance. It is what you do with this second chance that counts. Because there will be no third chance," Juncker said.

"Let's be crystal clear about the choice: it is this deal or Brexit might not happen at all," he said.

amp/aw (Reuters, AFP, dpa, AP)

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