Boris Johnson was in the royal box enjoying Saturday night’s Party At The Palace when the memo was being circulated.

       Titled 'Party Leadership' and written by an anonymous Conservative MP, the 758-word document was spreading like wildfire on Tory WhatsApp groups as the Prime Minister was enjoying performances by the likes of Rod Stewart and Diana Ross.

       Detailing the reasons why the man once dubbed "Big Dog" was "no longer an electoral asset", the excoriating document appeared to sum up the feelings of many backbenchers who feel their vote winner has turned into a vote loser.

       And it wasn't just 'partygate' and poor polling that had convinced them Mr Johnson was now in terminal decline.

       As the patriotic former London mayor was rubbing shoulders with the Royals, the last straw for colleagues appears to have been him being booed outside Friday’s service of thanksgiving at St Paul’s Cathedral.

       Citing a survey suggesting that 27 per cent of Tory voters think the Prime Minister should resign, the memo read: "The booing of Boris Johnson at the Jubilee Thanksgiving service tells us nothing that data does not. There is no social group that trusts him, with even 55 per cent of current Conservatives calling him untrustworthy, against only 25 per cent saying he is trustworthy."

       The so-called "greased pig" was slipping - even in the minds of patriots, it seemed.

       The damning memo predicted: "If left in post, will lead the Party to a substantial defeat in 2024. He will lose Red Wall seats (with majorities under 10,000) to Labour, and Blue Wall seats (majorities up to 20,000) to the Liberal Democrats.

       "At least 160 MPs are at risk (all majorities under 10k, and LD-facing majorities under 20k). Furthermore, tactical voting, so devastating in 1997, is returning and could turn a defeat into a landslide."

       Arguing that 'partygate' represented "a major breach of trust with the British population, including 2019 Conservatives, many of whom have abandoned the party already", it questioned Mr Johnson’s ability to win trust back, pointing out that a forthcoming investigation by the Privileges Committee could still prove damning.

       "The entire purpose of the Government now appears to be the sustenance of Boris Johnson as Prime Minister," it added, pointing out that "MPs are having to defend the indefensible, not for the sake of the party, but for one man".

       It also made the point that Mr Johnson "is the only Minister given negative ratings by activists in the ConHome ratings, meaning he is dragging everyone else down".

       Government policies had also proved unpopular, it argued, including the tax-and-spend measures announced on the cost-of-living crisis.

       The memo reached the stark conclusion: "The only way to end this misery, earn a hearing from the British public, and restore Conservative fortunes to a point where we can win the next General Election, is to remove Boris Johnson as Prime Minister."

       Now Sir Graham Brady has announced the 15 per cent threshold has been reached for a vote of confidence in the party leadership - it has emerged that Mr Johnson knew he would face a vote on Sunday.

       There is even a chance that he knew he would face a vote as he faced the flag-waving crowds in the Mall for Sunday’s Pageant, fearful, perhaps that he might be booed again.