Boris Johnson faces a Tory rebellion to stop a no-deal Brexit as he is on Tuesday expected to be crowned Prime Minister.
Johnson’s pitch for the top job has centred on leaving the EU by the end of October “do or die”, but he is already facing an exodus from his Cabinet if chosen by Conservative members over Jeremy Hunt.
Chancellor Philip Hammond and Justice Secretary David Gauke having already confirmed they will quit rather than be sacked by Johnson, and on Monday night International Development Secretary Rory Stewart confirmed he will stand down too.
Junior minister Sir Alan Duncan also resigned from the Foreign Office on the eve of the Tory leadership announcement.
Speaking at an event hosted by i newspaper, Stewart warned Johnson he would not have the numbers in the Commons to leave without a deal.
Stewart said Johnson would “not be able to get no deal through parliament because I have at least three friends”.
“There are at least five of us leaving the Cabinet, and there are many others too, who are against a no-deal Brexit and he has a majority of two,” he added.
It would leave Johnson as Prime Minister needing votes from other parties - specifically Labour Brexiteers - to get enough support.
It remains unclear whether Tory rebels would go further and attempt to remove the new PM from office.
After a Tory leadership race which began almost two months ago, and has included 17 hustings, interviews and two-head-to-head TV debates, the result is expected to be revealed late on Tuesday morning.
Party chairman Brandon Lewis will make a short speech before Dame Cheryl Gillan and Charles Walker – returning officers of the 1922 Committee – make the official announcement.
The new leader of the Conservative Party is expected to make a speech following the result.
But the new leader will have to wait another day to actually take office.
Theresa May will take her final Prime Minister’s Questions on Wednesday before formally resigning as PM.
She is expected to return to Downing Street after her last stint at the despatch box to have lunch and address Number 10 staff.
May will then make a short statement to media waiting before heading to Buckingham Palace to offer her resignation to the Queen.
The monarch will then meet the new leader of the Tory Party at the Palace and invite him to form a new government.
Traditionally, the new prime minister makes a statement in Downing Street before stepping into Number 10 for the first time as PM.
On Thursday, the new prime minister is likely to spend his first full day in office finalising his government with a reshuffle of the Cabinet and ministerial team expected.
Whoever wins the Tory leadership race will have to govern with a Tory-DUP majority of just two, as Charlie Elphicke had the Conservative whip suspended after being charged with sexually assaulting two women.
That majority could be further reduced to just one next week if the Tories fail to win the Brecon and Radnorshire by-election.