A defiant Boris Johnson has made clear he is not giving up his grip on power, despite pleas from ministers and Conservative Party MPs to step down.
No prime minister in modern history has attempted to cling to power in the face of such overwhelming opposition from his own side.
He places the ball firmly in the court of those who feel his position has become untenable.
– What can be done to remove Mr Johnson from No 10?
Initially, the focus will be on the Cabinet.
So far, most of Mr Johnson’s top team remain in their posts, although Home Secretary Priti Patel and newly appointed Chancellor Nadhim Zahawi are among those calling him.
The massive resignations from the Cabinet – accompanied by more resignations in the lower ranks – could be enough to force his hand if it makes him unable to form a functioning government.
However, there is no guarantee that will happen, particularly if the Prime Minister is determined to carry on with an exhausted administration.
– What else is there?
Then it is up to the Conservative MPs if they want to make another effort to oust him.
Traditionally, it would be up to Sir Graham Brady, the chairman of the 1922 backbench committee, to go to the Prime Minister and tell him that he has lost the support of his MPs and that he should leave.
If that fails, elections are held on Monday for the 1922 executive which is responsible for setting the rules of leadership.
Currently, Mr Johnson is shielded from another confidence vote for 12 months after surviving a challenge last month.
However, if still in place, the new executive will likely consider a rule change that could allow for a second confidence vote – possibly before MPs break for the summer later this month.
– If he lost such a vote, should Mr Johnson leave then?
That would mean he was absent as party leader – but not necessarily as prime minister.
Reports suggest he may refuse to quit a prime minister, but instead seek to call a snap general election – citing his tenure of 14 million voters in the last general election.
This would clearly be a nuclear option, which would raise a number of practical issues.
Some senior Tories believe senior officials would seek to dissuade him, warning it would be “inappropriate” to put the Queen in a “difficult position” by seeking a dissolution in such circumstances. But would he listen?
“So what’s the end of the game?”
Under the UK‘s unwritten constitution, any Prime Minister derives his authority from his ability to get his government’s business through Parliament.
If the government loses a major bill – especially a money bill – the prime minister will be expected to leave.
Alternatively, Tory MPs could join forces with the opposition to defeat him in a House of Commons vote of confidence – something they would normally be deeply reluctant to do.
And if all that fails, the country will truly enter uncharted waters.