When Matt Hancock drove to see Boris Johnson at Chequers to tell him he was resigning on Saturday, it wasn’t just an admission that he had run out of supporters after admitting his infamous clinch with an aide breached Covid guidelines. It was also a rare moment when the prime minister’s legendary ability to defy political gravity appeared to falter.

Even by Saturday afternoon, when Tory MPs had begun to make their feelings known, Hancock’s own local paper had condemned him and senior figures in the NHS had concluded Hancock had lost all credibility, Downing Street stuck to its initial conclusion that the matter of the health secretary’s conduct was closed. The tactic, after all, had a good record of success. Be it the home secretary Priti Patel over bullying claims, education secretary Gavin Williamson over botched exams, or communities secretary Robert Jenrick over a Tory donor’s property deal, Johnson resolutely ignored demands for sackings. The regular use of the tactic had led Whitehall insiders and some Tory MPs to wonder what levers were still in place to hold faltering ministers accountable.

Yet it was the health secretary who concluded that the tactic could not save him. The previous 48 hours, and the collateral damage caused by the exposure of his alleged affair with his aide Gina Coladangelo, had left him with little doubt.

It was a vaguely absurd vignette on Friday night that demonstrated how little support Hancock had remaining. With his career hanging by a thread, facing a series of unanswered questions over hypocrisy and propriety following the exposure of his office clinch with Coladangelo, he faced an online meeting with 70-odd members of his local Tory party – and they weren’t happy. “He broke the rules when many of us weren’t allowed to see people we love dearly,” said one member. “Everyone is shocked. There is a lot of grievance. We were not seeing family. He’s told us to do that and we’ve followed him, and then you find out rules don’t matter to him.”

The embattled Hancock was spared an uncomfortable questioning by a friend. Members said that the chair, Rachel Hood, a Hancock supporter who donated £10,000 to him in 2018, did not allow any questions after he had given them all an update, largely on local issues. But the fallout continued.

By Saturday morning, the pressure on Hancock was intensifying, again in his own backyard. One local paper, the Eastern Daily Press carried the headline, “A complete and utter hypocrite”. Duncan Baker, a Norfolk MP, became the first Tory to call for his resignation. Meanwhile, there was also growing anger in the NHS, with influential figures amazed that Hancock had, at first, opted to stay and fight it out. “It is really difficult to see how somebody who has done what he has done can lead with credibility and authority,” said a senior NHS source. Tories reported to their whips that, much like Dominic Cummings’s trip to Barnard Castle, Hancock’s rule-breaking office clinch risked a major breach in public trust.

His resignation letter, sent to the prime minister on Saturday evening, was an admission that even if he had weathered the initial storm, he had lost crucial credibility. “We owe it to the people who have sacrificed so much in this pandemic to be honest when we have let them down,” he wrote. He could not hold the No 10 line. The support he subsequently received from Tory MPs was, to some extent, a sign of relief in the party that accountability still had some hold over the cabinet.

Downing Street’s hopes of simply closing down the issue were stymied by obvious questions. Coladangelo, a PR expert who had been a director of a lobbying company, was hired last year first as an unpaid adviser, and then as a paid non-executive director at Hancock’s department. Those appointments came with no public fanfare, while there was seemingly no independent process for her appointment as a director.

Meanwhile, more revelations emerged. On Saturday night, government sources confirmed that Coladangelo accompanied Hancock to the G7 meeting of health ministers in Oxford this month, with the department paying costs. The source said she was there in her capacity as a non-executive director with board oversight for international policy, and that the department paid for the whole delegation. Insiders suggest that she was acting more as a special adviser. There are already a series of demands for inquiries over how Coladangelo was appointed, including how she came to have a parliamentary pass sponsored first by Hancock in 2019 and then by health minister Lord Bethell.

In reality, many in the health service and political world concluded on Saturday morning that the growing charges against Hancock would simply weigh him down in the job. He had faced accusations of lying from Cummings, the prime minister’s former aide, who suggested Hancock’s handling of the pandemic, especially over PPE, testing and care homes, meant he should have been sacked several times over. Further revelations from Cummings last week showed the prime minister despairing of Britain’s pandemic response last year. Hypocrisy is the other glaring charge, most obviously in relation to Hancock’s conclusion last year that the scientist Neil Ferguson had no choice but to resign from the government’s science advisory committee over breaking lockdown rules. It left him few friends in the scientific and health fields.

Then there are the imminent health service reforms that Hancock was due to present to some cabinet colleagues on Monday, before introducing them in the Commons. Like all changes to the NHS, they are proving controversial, but the main bone of contention is the extra powers that will flow to the incumbent health secretary. Insiders were already asking if the new bill, an immediate challenge for new health secretary Sajid Javid, should proceed as planned. “It feels a bit rich that on the one hand, he should be asking for extra power, and then on the other, basically showing behaviours that are completely incompatible with the increased power that he’s asking for,” said a senior NHS figure.

Some Tories thought Hancock could survive had he made it to the Batley and Spen by-election, when the focus will switch to Labour. However, the obvious lack of support, with the threat of more fallout in the days ahead, made Thursday seem a long way off.

And what of accountability in the age of Johnson? Opposition parties are already hoping that Hancock’s demise is a sign that, even with an administration as unusual as Johnson’s, gravity will always find a way to bring matters back to earth.