A simple interactive guide to what could happen next as the UK leaves the European Union.

At least 48 letters have been sent to the chair of the 1922 Committee, triggering a vote.

The Irish PM says the DUP is focused on a Brexit deal that respects the integrity of "the precious union".

Another episode of Brexit drama unfolded in Westminster and Brussels.

It started with the new work and pensions secretary Amber Rudd saying a no-deal Brexit would not get through Parliament, apparently undermining Theresa May's insistence that that was an option if MPs didn't back her Brexit plan.

It continued with Theresa May and Jeremy Corbyn locking horns over Brexit at Prime Minister's Questions.

It ended with Theresa May booking another return ticket to Brussels as she said she would come back for further talks on Saturday in a bid to clinch a final deal ahead of a key summit of European leaders 24 hours later.

As it stands, Sunday's meeting to sign both the withdrawal and declaration agreements is still due to take place despite last-minute hitches, including Spanish concerns over how future trade relations will apply to Gibraltar.

The arrangement is "not just about money" but also "making sure the union is secure", warns the DUP leader.

Theresa May is to return to Brussels for last-ditch Brexit talks on Saturday as the two sides try to do a deal in time for a summit of European leaders.

The PM said progress had been made during discussions with EU officials on Wednesday and work would continue on outstanding issues.

She said she hoped to reach a deal soon "in the interests of all our people".

Talks over future relations have been held up by concerns over fishing rights and the future of Gibraltar.

The EU is in a race against time to complete the text of its declaration on future relations with the UK, amid concerns from several member states.

German Chancellor Angela Merkel has indicated she will not attend Sunday's meeting of European leaders - which has been called to approve the draft terms of the UK's withdrawal - unless the text on future co-operation is agreed in advance.

After an hour of talks with European Commission President Jean-Claude Juncker, Mrs May sought to strike an upbeat note but signalled talks were set to continue until the eve of Sunday's summit.

"We've made further progress and as a result we have given sufficient direction to our negotiators, I hope, for them to resolve the remaining issues and that work will start immediately," she said.

"I now plan to rerun for further meetings on Saturday to discuss how we can bring to a conclusion this process and bring it to a conclusion in the interests of all our people."

Read the developing story here

Carwyn Jones has "better than expected" meeting with the PM but says some areas need more work.

The PM holds talks with Jean-Claude Juncker as a cabinet minister says MPs won't allow a no-deal Brexit.

Image source, PA

Leo Varadkar has said the DUP has put the integrity of the "precious union" ahead of everything else, even if it leads to a "lesser world".

The Irish Taoiseach said the party - which is in a confidence and supply agreement with the Conservatives - did not want the "best of both worlds" from Brexit.

He told the Irish parliament: "The DUP holds very firm to this view that the most important thing is the integrity of the UK, the integrity of the precious union, and, if that means a lesser world, that's acceptable provided that the integrity of the union is upheld."

Mr Varadkar added that the withdrawal agreement should not be seen by unionists as a threat to the UK.

"It shouldn't be seen as any effort to separate Northern Ireland from Great Britain," he said.

Jeremy Corbyn asks Theresa May at Prime Minister's Questions if she agrees with colleagues that "there are no circumstances under which Britain will leave the EU with no deal?"

Caroline Lucas calls for another Brexit vote at Prime Minister's Questions, saying the "will of the people has changed", but Theresa May says this is "absolutely ridiculous".

Image source, PA

An official from HM Revenue and Customs has told MPs it will take two years to have a fully operational customs system at the UK border if the UK leaves the EU without a deal.

Senior official Jim Harra told the Treasury Select Committee they were ready to have a functioning border from 29 March, but it would be a "clearly sub-optimal customs border".

He added: "There would likely be some fiscal risk attached to that depending on what tariff decisions are.

"I think we are looking at a minimum of two years from the no deal to get to a point where you can say we have a steady-state system where we are comfortable that we can manage all the fiscal risks in a way we would like and trade can flow in the way we would like".

The chief executive of HMRC, Jon Thompson, also told MPs: "The date for putting in an optimal customs system for the UK in the event of no deal was passed months ago."

Kevin Connolly, BBC Europe Correspondent
BBC Radio 4's PM

Angela Merkel has been quoted as saying she won’t come to the EU summit on Sunday unless there is a document to sign.

The idea of these summits is the leaders don’t come to haggle or horse trade - they come to clinch the deal, sign off on it, to make it a public piece of history.

So that is why they say if it is not finished they wont be here.

But people in Brussels who have been around a long time will say that, in the end, there is always a deal.

This is only about making a framework for talks on a future relationship between the UK and EU, which will start once the UK is no longer a UK state – after 29 March 2019.

It ought to be possible by massaging the wording to keep everyone, if not happy, then at least on-board.

My suspicion is that as things stand tonight, that will still happen, but it is also still possible that things will continue to slip.

Image source, Houses of Parliament

Earlier, Labour's Steve Reed became the first frontbencher to publicly back a referendum on the Brexit deal.

The party's shadow Brexit minister, Jenny Chapman, said the mood within Labour towards a public vote was changing.

She told the BBC: "There is growing enthusiasm for another referendum, because there's such concern about this vote that's about to happen, and about making sure that we don't leave without a deal.

"So, the Labour Party's position is that having another referendum is something that we'd keep there as an option.

"But the first thing is... let's look at the deal and let's have this vote."