After the vote of confidence was announced, many predicted that Boris Johnson would survive it.

However, when the Gray Report was published the consensus was "he was safe for now". It was said that it had not changed people's minds about Mr Johnson and would not provoke a challenge. Opinion polls taken in the immediate aftermath seemed to bear that out.

The public reaction to big reports like Ms Gray's can take a while to come to surface though and it was clear from the past week that the public mood towards the prime minister had darkened, particularly the reports of rudeness to security and cleaning staff during the Downing Street parties.

Mr Johnson was booed by a section of the crowd at a Thanksgiving Service at St Paul's Cathedral last Thursday - something unheard of during Jubilee celebrations.

Now there is a confidence vote and the consensus seems to be from Tory sources, including some rebels that the numbers are not there for it to succeed.

It only took 54 MPs to get the confidence vote but it will require 180 MPs for it to succeed.

It has been pointed out that 171 of them are currently Johnson appointees in various government roles ranging from ministers to ministerial aides.

Many of those appointees, including potential leadership contenders such as Foreign Secretary Liz Truss and Chancellor of the Exchequer Rishi Sunak, have been out in support of the prime minister.

Rishi Sunak has been out in support of Boris Johnson

The speculation has been that Mr Johnson retains the support of around 60% of the 359 Conservative MPs. And those who support him have been on message: that it would be the wrong time to change leader, that he got the big calls right such as the vaccine rollout and the Ukraine war.

However, it is a secret ballot and the momentum has been against Mr Johnson in recent weeks. Former health secretary Jeremy Hunt has come out against Johnson.

And even if he does win the vote, it may fatally damage his leadership anyway.

Theresa May won a no confidence vote six months before she felt she had to resign as leader.