Why MPs could move against Rishi Sunak as soon as this week - analysis by Christopher Hope

So the big question is what happens next. The MP could see two options: Sir Graham Brady, the chairman of the 1922 committee, leads a delegation to No10 to read the riot act. "But I am not sure that will work," the MP told me.

The second option is more alarming for Tories: that enough no-confidence letters are submitted in Sunak's leadership to past the 53 threshold to trigger a vote of no confidence in his leadership.

This latter option is the more likely. Two other Tory MPs told me today that around 40 no-confidence letters have been submitted. A former whip told me that "half a dozen" letters were submitted over this weekend.

Rebels who want the PM replaced are worried that a 'disordered' no-confidence vote will just shore up his position as happened with the 2018 no-confidence vote in Theresa May's leadership, when a snap vote was held by Brady before the rebels were ready.

What is very clear today is that something changed in the Tory Parliamentary party late last week, in the wake of the defection of Lee Anderson - who was then an Independent - to the Reform UK party, and the row over comments about Diane Abbott by a donor.

Conservative MPs are now campaigning for their party's councillors at the May 2 local elections (the official 'purdah' period for the London Mayoral elections starts on Tuesday this week, and next week for the local elections in England and Wales), and so are finding for themselves the antipathy towards the Tories on the doorstep.

The party's options are limited. I have written before about the idea of a 'Contract with Britain' plot to replace Sunak with Penny Mordaunt and a promise of a General Election after 100 days.

Certainly, the Tories have replaced a leader before when a General Election was in view (Sir Iain Duncan Smith in 2003) but polling day was never this close.

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Mordaunt is favoured by Tories to take on Labour leader Sir Keir Starmer; Labour MPs tell me they fear her the most.

But plenty of Tory colleagues on the Right worry that she is too much of a blank canvas who may not be the sort of Conservative they want to lead the party.

Something has got to give. When I asked today a moderate Tory MP what were Sunak's odds of making it to the November General Election as PM, he replied: "50-50." Until today I thought talk of replacing Sunak before the election was crazy; I don't any more. And it could all happen in the next seven days.