Boris Johnson’s fate will be decided in Committee Room 10, deep within the Palace of Westminster, where Tory MPs cast their votes.

The MPs have been ordered to surrender their phones to preserve the secrecy of the confidence vote process after two broke the rules to take photos of their ballot papers during the 2018 decision on Theresa May’s leadership, a Conservative source said.

MPs will file through the committee room between 6pm and 8pm to vote with the ballots then counted by the officers of the 1922 Committee.

The Prime Minister will be informed of the result shortly before the formal announcement, which will be made just down the committee corridor in Room 14 at 9pm.

MPs unable to vote in person will be able to nominate a proxy to cast their ballot.

The whole process will be overseen by Sir Graham Brady, chairman of the 1922 Committee, who said he runs a “tight ship” – he was also in that position when Mrs May faced the same ordeal during her turbulent leadership.

Sir Graham broke the news to Mr Johnson that he would face a confidence vote early on Sunday afternoon.

The threshold of 54 MPs calling for a vote had been passed on Sunday and Sir Graham said he had received a “clear indication” from other MPs that they would be submitting letters on Monday following the conclusion of the Platinum Jubilee festivities.

Should Mr Johnson lose the confidence vote then his leadership of the Tory party will end – triggering a contest to replace him which could last for around two months, as the process which led to his election did.

However, that process could be significantly curtailed, as it was when Mrs May became prime minister and her final rival Andrea Leadsom dropped out.