As more Conservative MPs go public with their letters of no confidence in Boris Johnson, the chance of a vote on the prime minister’s premiership grows. This is how the process works:

How is a vote triggered?

The rules stipulate that 15% of Conservative MPs must submit a letter of no confidence to Sir Graham Brady, chair of the backbench 1922 Committee, in order for a ballot to be held.

The MPs do not have to reveal their identity, though some will choose to go public due to pressure from their constituents or in a bid to encourage others to do the same.

There are 54 MPs needed to force a vote of no confidence, and they can either deposit a letter personally to Brady’s office, ask a colleague to drop it off for him or email it directly.

The only person who knows how many letters have been submitted is Brady himself. Such is the level of mistrust among Conservative MPs, several rumours have been spread to discourage people from submitting no confidence letters.

Brady does not – as it has been claimed – need to ring every Conservative MP who has submitted a letter to check they are happy with their decision. Nor does he – as others have suggested – pass a list of those who have submitted letters to Johnson’s ministerial aides, known as parliamentary private secretaries.

There have also been rumours that government whips have previously been posted to keep watch outside Brady’s office, to spy on those going in and out.

What happens if the 54 threshold is hit?

There is a certain amount of discretion afforded to Brady, but he is expected to tell the prime minister and then organise a private confidence vote “as soon as practicable”.

Most MPs agree it is not practical to hold such a ballot during recess, which ends next Monday, and particularly not during the Queen’s Platinum Jubilee bank holiday weekend.

In December 2018, Brady told Theresa May the threshold had been hit and a vote was held on her premiership the following day. The speediness of the procedure was seen as a bid to give as little time as possible to her opponents to organise against the current government.

How is the vote organised?

A ballot box is being safely stored in the office of one of the 1922’s executive members, and will be dusted off if a no confidence vote is called.

It will probably be placed in the same room that MPs gather in every week for meetings of the committee, on the first floor of the Palace of Westminster and at the centre of a long corridor, overlooking the River Thames.

Throughout the day, all Conservative MPs will be able to vote in a secret ballot. They will be forbidden from taking any pictures inside the committee room. This is meant to discourage party whips from demanding photographic evidence that an MP has voted supportively, meaning that even if they are on the government “payroll” they are able to decide freely whether to vote for or against Johnson.

That is not to say that supporters and opponents of the prime minister will not spend the day frantically lobbying and counting the pledges of each MP collared to ask how they voted.

If an MP is away from Westminster, they can nominate a colleague to vote on their behalf as a proxy.

How is the result announced?

Brady will probably do as he did in 2018, and assemble MPs and journalists in the same parliamentary committee room where voting has taken place that day. He will then declare that the parliamentary party does or does not have confidence in the prime minister, and reveal the number of votes cast in both directions.

If Johnson survives, no further confidence vote can be held by the 1922 Committee for another year.