Sir Graham Brady once quipped that the pile of letters calling for a vote of no confidence in the prime minister always had “an element of traffic in both directions”. “It isn’t like a thermometer outside the local hospital showing how much money has been raised.”

The MP for Altrincham and Sale West, who is the “shop steward” for Tory MPs as the head of the 1922 Committee, may become its first chair to oversee two votes of no confidence, having been in the post for more than a decade.

If the threshold of 54 letters given to him is reached this week, the timing of an announcement will be his decision. He must also be sure of the letter-writers’ intentions. On the eve of Theresa May’s confidence vote, he recalled, letters were still being submitted and withdrawn, but he judged that the threshold had clearly been crossed.

Even then, mindful of his image as a paragon of discretion, he did not disclose to May exactly how many letters over the threshold had been given to him when he phoned her just after 9.30 on the evening before the vote.

She survived the challenge, but Brady’s power only grew. As pressure increased for her to name a date of departure, Brady visited the prime minister and told her he had a letter containing the result of a vote from the 1922 executive on whether to change the rules to allow for another confidence vote to take place. He did not disclose the result of the vote. She named a date.

In the paranoid world of Westminster, there are always fears about leaks, but no letter has ever leaked in the past and Brady always emphasises his sensitivity – with a smile that often suggests he enjoys the position of intelligence that he holds. None of Brady’s staff have any access to the letters or emails.

He has also tactfully warned excitable journalists and MPs to be mindful of declarations made in public, recalling several instances when MPs had declared publicly they had sent a letter, or withdrawn one, or would never send one, when the opposite was true.

Despite the seriousness with which Brady takes his neutral role as chair, he has not shied from rebellion and has been a vocal critic of Johnson’s lockdown policies and May’s Brexit deal, in a break with the convention of previous chairs of the committee, who largely refrained from public comment on policy.

A forthright Brexiter, he initially voted against May’s withdrawal agreement, though he relented at the final time of asking. In the frenzy of the Brexit votes, his name went on a successful amendment, backed by the prime minister, to replace the backstop with “alternative arrangements” – an amendment that meant nothing and went nowhere.

He is also not without ambition and is rumoured to be considering a run as a dark-horse candidate for the leadership. He is close to other Johnson critics, including Mark Harper and Steve Baker, who might be influential in deciding the next leader.

Brady took the unusual step of recusing himself from overseeing the leadership race that led to Johnson’s coronation. His absence was ostensibly because he was planning to run as a candidate himself, but he never launched a campaign.

During the pandemic, Brady became one of the most fervent MPs speaking out against Covid lockdown policies, saying the country had been “terrorised” by restrictions that he said were draconian and illogical.

Relations between Brady and Johnson became irreparably strained after whips gave tacit support to an attempt last year to replace him as chair of the 1922 Committee with a more favourable candidate, Heather Wheeler. Brady saw off the challenge, which most MPs saw as transparent in its intent.

With the Covid lockdowns debate behind him, Brady has not recently spoken out on any new policy divergence with the prime minister, but he would be forgiven for being nervous about his own position – his Greater Manchester seat is a key target for Labour.