He had to go. It was inevitable. The charge sheet against Sir Gavin Williamson was getting longer, not just by the day, but by the hour.

It was impossible for him to survive, given the damage the bullying row was doing to Rishi Sunak.

Did he jump or was he pushed? Despite Sir Gavin claiming in his resignation letter that he had become a distraction, he was almost certainly pushed.

Reaction as Williamson forced out for third time – politics live

The prime minister who promised accountability and integrity on the day he succeeded Liz Truss had clearly decided enough was enough.

Earlier, Number 10 said Mr Sunak still had full confidence in Sir Gavin and believed his denials – but that was always too risky. Many Conservative MPs were questioning whether the damage to the prime minister was worth it.

It was always likely that Sir Gavin would go before this week’s prime minister’s questions.

Last week, Sir Keir Starmer tormented Mr Sunak with a powerful onslaught on his reappointment of Suella Braverman as home secretary six days after Ms Truss sacked her for a security breach.

The PM didn’t want a repeat of that sort of painful experience at his high noon with the Labour leader this week, especially since his appointment of Sir Gavin was arguably even more reckless than the home secretary’s swift return.

The charge sheet – which the former director of public prosecutions will no doubt read to the jury of public opinion at PMQs – begins with Sir Gavin’s abusive and threatening texts to former chief whip Wendy Morton about not being invited to the Queen’s funeral.

Laid bare in excruciating detail in The Sunday Times, they included the menacing: “Don’t forget I know how this works so don’t puss me about”, “let’s see how many more times you **** us all over”, and “there is a price for everything”.

Then on Monday, The Times reported that a government minister claimed that when Sir Gavin was chief whip, he raised details about her private life in a conversation in an attempt to silence her when she was on the backbenches.

Thirdly, The Guardian reported that a former senior civil servant claimed Sir Gavin told them to “slit your throat” and “jump out of the window” in a sustained campaign of bullying, in which he “deliberately demeaned and intimidated” them on a regular basis while he was defence secretary.

Ultimately, and crucially, that civil servant – after seeing the texts to Wendy Morton – turned up the heat on Sir Gavin by reporting his behaviour at the Ministry of Defence to the Independent Complaints and Grievance Scheme (ICGS), the parliamentary watchdog, claiming his words and actions had an extreme impact on their mental health. That could be a slow process, however, as Ms Morton may also discover.

As chief whip, Sir Gavin revelled in his reputation as a menacing enforcer in the style of Michael Dobbs’ chief whip Francis Urquhart in House Of Cards. The real life chief whip even famously kept a tarantula called Cronus on his desk.

After the “slit your throat” allegation, as Downing Street and fellow ministers struggled to defend Sir Gavin, the most hilarious attempt at backing for him came from Mel Stride, the newly appointed work and pensions secretary.

“The reality with Cronus is he was much touted but he never actually was released to bite anybody,” he told Kay Burley on Sky News. Oh, that’s OK then.

Nicky Morgan, the former Tory cabinet minister, told a different story in a TV interview: “I had my run-ins with Gavin Williamson when he was Theresa May’s chief whip. None of this surprises me, sadly. This is a story that is going to keep on giving.”

That was always the case. And that was the problem for the prime minister. The consensus among MPs is that he only handed Sir Gavin his comeback as a reward for a political crony who helped him – eventually – win the Tory crown.

Another view among Tory MPs is that Sir Gavin’s post as minister of state in the Cabinet Office, sweetened by the perk of attending cabinet, was effectively a non-job with no departmental responsibilities.

In reality, though, he was in the Cabinet Office as an enforcer and fixer for the PM. It was the same job that cricket-loving Tory MP Sir Nigel Adams did for Boris Johnson.

And in a further example of cronyism, Sir Nigel has now been nominated for a peerage by Mr Johnson as a reward for batting for his old boss.

One seemingly preposterous conspiracy theory being put about by allies of Sir Gavin is that the attempts to discredit him were all a plot by friends of the ousted Ms Truss.

The theory went that it was Sir Jake Berry, Tory chairman under Ms Truss and another close ally of Mr Johnson, who instigated an inquiry inside party HQ into Sir Gavin’s expletive-laden texts to Ms Morton.

However, Ms Morton – one of Ms Truss’s closest allies – has now escalated her bullying complaint, fearing a whitewash by the Conservative Party, it’s claimed. A whitewash in a bullying inquiry? What a suggestion!

Ms Morton has also referred Sir Gavin to the ICGS. But many in parliament regard the ICGS – set up after the so-called Pest-minster scandal – as useless and toothless.

Its latest annual report, published – conveniently – in the period between Ms Truss’s resignation and Mr Sunak becoming Tory leader – revealed that it took an average of 196 days to conclude an investigation.

That’s more than six months. Painfully and inexcusably slow. And talk to any Commons staffers who have accused an MP of bullying and they’ll also tell you the process is rigged in favour of the accused, not the accuser, and MPs are judge and jury in the process.

So for Sir Gavin, the bigger threat to his remaining in his Cabinet Office “non-job” than an ICGS investigation was always going to be the charge sheet against him getting even longer in the coming days.

Ominously for Sir Gavin, hours before his resignation Mr Sunak signalled he may not wait for the results of the two inquiries before acting.

That’s clearly what happened. His protector, the prime minister, obviously lost patience with him and decided to call time on Sir Gavin’s comeback.