How resignations could impact PM
What do the resignations of Boris Johnson and David Davis mean for Theresa May, and how damaging is this to the Prime Minister?
This is a massive blow. The Prime Minister would have been forgiven for thinking on Sunday evening that she had managed to placate unhappy Cabinet Brexiteers at Chequers on Friday. Now she has lost the seventh and eighth ministers from her Cabinet since last year's election, in less than 24 hours. They are the first to quit over a fundamental difference on her Brexit platform; one of them was in charge of implementing that policy.
However, Mr Davis has said he is not seeking to trigger a coup to remove the Prime Minister, and Downing Street insiders indicated he was seen as doing "the honourable thing" in light of Mrs May's announcement that the doctrine of strict collective responsibility was being reimposed on Brexit. What Mr Johnson plans to do remains to be see.
Does it mean the end of Mrs May's premiership?
This is far less certain than some of her opponents appear to believe. In order to oust the Prime Minister as Tory leader, some 48 Conservative MPs would have to send letters demanding a vote of no confidence.
There are believed to be around 60 backbenchers in the Eurosceptic European Research Group (ERG), along with many others who would like to see a "harder" Brexit than the version set out at Chequers last week, making her vulnerable to an anti-EU revolt.
However, the ERG's chairman Jacob Rees-Mogg has said he has not sent a letter to the 1922 Committee, and expects Mrs May to remain in office at least until Brexit day in March 2019. Others may take their lead from him.
Why wouldn't they want to challenge Mrs May?
There are a number of issues that may make Eurosceptic critics hold back from an attempt to unseat the PM.
Aside from the loyalty which MPs naturally feel towards their leader, many are concerned that Mrs May's removal could plunge the party into chaos, with no obvious replacement lined up, potentially setting the scene for Jeremy Corbyn to seize power in a new general election.
Some Brexiteers think that the most crucial issue is to ensure that Britain actually leaves the EU in March next year, and feel that whatever arrangements Mrs May has secured can always be renegotiated once that point has been reached.
Could that change?
This is a possibility, particularly now Mr Johnson has followed Mr Davis out of the door. A fracturing of unity at the top of the party could test the loyalty of rank-and-file MPs, many of whom have spent the weekend listening to complaints of betrayal from pro-Brexit constituents. Mr Johnson's ambition to occupy Number 10 is well-known and he is popular with Tory rank-and-file members.
What if she does face a vote?
It is far from clear that Mrs May would lose any vote of no confidence. Rebels are by no means certain of securing the backing of 159 Tory MPs which they would need for a successful coup.
However, a narrow victory would leave Mrs May as a wounded premier and would raise doubts over the viability of her being able to remain in office.
What does it mean for Brexit negotiations?
Mrs May has said that she wants talks to go ahead with greater intensity and pace once Britain has set its position out in the white paper due for publication later this week.
European Commission president Jean-Claude Juncker promised that the EU would "continue to negotiate in good faith", while his chief spokesman said Mr Davis' departure would not affect the approach of Brussels, saying: "We are here to work."
However, Mrs May's ability to squeeze concessions out of Brussels is likely to be undermined if the Commission and the 27 other member states doubt her ability to get her proposals through Parliament.