One Tory MP called him an “unelected, foul-mouthed oaf”. Former prime minister Sir John Major said he was “a political anarchist, who cares not a fig for the future of the party”. And now David Cameron has come up with what for him is perhaps the most damning insult of all: a “bad spad” [special adviser].

Yes, Dominic Cummings is a bad spad and dangerous to know, to paraphrase Cameron’s new memoir. In his book, the ex-premier accuses Cummings of deploying “bilious briefings” to the media and “dripping poison” into the ear of his former boss Michael Gove.

Cameron (a former special adviser himself) relates how he “totally flipped” one day in 2013 when Gove, egged on by his former spad, tried to back out of an agreement to be reshuffled from education secretary to chief whip.

We now know that Cameron texted Gove: “Please don’t become a wanker”. Gove complied, but it’s clear that the former PM still regards Cummings as the epitome of political self-love.

For Cummings and his allies, all the criticism merely confirms he’s doing something right: irritating the hell out of the establishment he so loathes.

Installed last month as Boris Johnson’s chief adviser and strategist, the man who masterminded Brexit’s Vote Leave campaign in 2016 now has more power than ever before.

But with the Supreme Court due to rule on the legality of a five-week suspension of parliament which many suspect was Cummings’ brainwave, just what makes this 47-year-old political maverick tick?

And what role if any will he have beyond the Halloween deadline that Johnson has set himself for the UK’s exit from the EU?

Cummings has been dubbed “Boris’s Bannon” by some MPs, a reference to Donald Trump’s former consigliere Steve Bannon.

Just as Johnson (Oxford graduate, Classics lover, encyclopaedic memory) is way smarter than Trump, Cummings (Oxford first class graduate, data freak, maths and physics obsessive) is in many ways much smarter than the autodidact Bannon.

But the two disrupters-in-chief do share several traits. They both make no secret of their loathing of their country’s governing party, they have a fascination with revolutionaries and artificial intelligence, and they love goading their opponents.

Cummings lacks the former Breitbart chief’s openly racist white nationalism, though critics say  his willingness in the Vote Leave campaign to parade the spectre of millions of Turks heading to the UK proved he’s not beyond dog whistling.

In new extracts from his memoir published in the Sunday Times, Cameron lets rip at Cummings’ boss Gove for indulging such a “foam-flecked Faragiste”. He seems even more withering about Cummings himself, saying he brewed a “cauldron of toxicity” and he and Farage had “something of the night about them”.

The irony is that Cummings also viewed Farage as too toxic to be allowed near the official Leave campaign, and insists that’s precisely why it managed to win over middle-of-the-road waverers.

Some Tories believe that proves his sin was more insidious: he used a sly Turkish dog whistle on immigration rather than a Ukip-style megaphone like the ‘Breaking Point’ migrants poster.

Still, he’s well used to being depicted as an evil genius and his friends are mildly amused by recent anti-Brexit campaigners’ placards depicting him with horns on his head. One poster even used an online Game of Thrones meme, with the headline “Winter is Cummings”.

And it’s the internet where Cummings still loves to mix it. Only this week, the Tory party has said it is reviewing its Facebook ad policy after complaints that it misrepresented a BBC story about education spending.

Whereas the BBC reported schools would get a £7bn cash boost, the Conservative advert superimposed a headline stating it would be a record £14bn.

One former colleague says the row – like the controversy over the Treasury hailing duty-free cigarettes and booze post-Brexit – was a carefully designed controversy to generate even more publicity. “It felt like classic Dom,” they say. And the education theme was no surprise, given Cummings’ own tenure for six years advising Gove in opposition and government on schools policy.

In fact, an ex-insider recalls a little-noticed episode that exemplified the Cummings modus operandi at the time.

While in government, he commissioned a short ‘movie’ that highlighted all of Gove’s achievements as education secretary. As taxpayers’ money was used, rather than party funds, Cummings deliberately designed the film to cause a row over politicisation of Whitehall. On that occasion, however, the tactic flopped as few even noticed the propaganda film.

It was during his Department for Education stint that Gove’s spad refined his combative approach.

Once, when there was a particularly critical report beginning to make headlines, aides were told to go on the attack and tell journalists it was ‘hysterical nonsense’. Within seconds, that phrase appeared on a 24-hour TV channel strapline, and the report was downgraded on bulletins.

“He’s certainly extremely outcome-focused and goal-focused, there’s a single mindedness about him,” one former colleague says. “When he does have a fight with someone, it’s recreational.

“He enjoys what might be called a knife fight. But he’s not someone who seeks confrontation for the sake of it.”

Others felt that the fights got in the way. Sam Freedman, who was a senior policy adviser who worked for Gove, says: “I think one of his flaws is that he can’t leave petty battles alone.

“That’s obviously a distraction from the business of trying to do a big reform programme in the education department. And I think you can see it again, happening a bit now. Dominic Grieve is someone he really, really doesn’t like and has never liked.

“And I feel he’s got a bit caught up in the fight with some individuals rather than stepping back and looking at the big picture.”

Another ex-colleague says: “The big question is whether he is just a supremely good tactician or is he a strategist too? He sees himself as a strategist.”

One case in point was Cummings’ botched attempt to abolish GCSEs, replacing them with an O-level-style qualification for higher achievers and a lower grade exam similar to the old CSE for the less academic. The plan was leaked to a Sunday paper but within days the backlash was fierce as critics warned of a return to a two-tier exam system.

Deputy PM Nick Clegg rang Cameron to complain and within 10 days the whole thing collapsed. Cummings still believes it was Gove’s biggest failure not to push ahead with it.

Yet others in government felt that in the end a much smarter course was pursued. GCSEs were indeed reformed and made tougher, course work was scrapped, new grades were added to the top end – but without any of the ‘two-tier’ political quagmire.

One of Cummings’ big successes, however, was the creation of specialist sixth form maths schools, in London and in Exeter. Within a few years, they have already outperformed most private schools in their results and university placements, while taking in a diverse mix of students.

A history graduate himself, Cummings hired a maths tutor to get him up to postgraduate level in the subject, and wanted to create a UK version of the Kolmogorov Physics and Mathematics School in Moscow.

A colleague recalls: “Whenever he was going through a particularly difficult time with problems piling up in the DfE, you would often hear him say, ‘Right I’m off to work on the maths schools, I’ll be alright after that’. He would then spend three or four hours on it.

“What is refreshing about him is he is utterly free of nostalgia, is totally future facing. He really does have a vision of Britain as the best place in the world to do science and be educated.”

One other idea, a new, non-A-level qualification for 16 to 18 year olds for ‘maths for everyday life’, didn’t get off the ground. It was meant to combat statistical illiteracy in wider society.

For some, that sums up Cummings’ contradictions: the man who used for political gain the gross rather than net EU spending figure (that £350m a week) is also the man who wants to educate the nation to avoid basic maths errors.

And the fight-picking is never far away. Nick Clegg once said he has “obviously got some serious anger management issues”. In 2014, Cameron famously said Cummings had moved from “policy wonk, to special advisor, to career psychopath”.

But for Freedman, Cummings got many things right. “I think he has a very acute understanding of the flaws with the British state, and a very good understanding of why things don’t work very effectively in government. And that informs his desire to kind of smash through a lot of arcane and bureaucratic processes that he thinks gets in the way of decision making.”

He also thinks the ministerial ‘red box system’ of Whitehall is a relic of the Victorian era, a point many would agree with. No private sector firm sends their CEO home at the end of every day with a list of minor decisions that have to be ticked off at home over a couple of glasses of wine, he told friends.

Cummings was also the one to spot straightaway, for example, that Free Schools could end up with the freedom to award huge head teacher’s salaries, and moved to counteract it.

That knack for how the public would react was underscored back in 2008. “He was very, very quick to realise how angry people would be about the expenses scandal, probably faster than anybody else I knew in Westminster at the time,” Freedman recalls.

“I think Michael Gove could have been in more difficulty with that story had Dominic not done a lot of the stuff he did, to sort of get out in front of that story.” (Gove held a public meeting apologising to his Surrey Heath constituents and paid back key expenses).

However, Chris Cook – the former FT journalist who reported extensively on the Gove-Cummings era – says that Cummings’ desire to smash the system often runs up against not just petty bureaucracy but also the normal checks and balances designed to prevent abuse.

“I think the line from there [the DfE] to where we are today is that, that is basically a believer in executive power. He doesn’t feel constrained by the institutional mores that other people do.

“I think there’s a thing about him and empathy. He’s intensely self confident. And he fundamentally believes an argument that’s convincing to him will be convincing to everyone else.

“And that’s why, by the way, I think he keeps losing court cases, because he can’t see the weaknesses in his own arguments. But  also he doesn’t understand other people’s motivations.”

Freedman adds: “When you’ve got barriers in the system that are there for no particular reason, then you need someone who’s got a bit of belief in in smashing those things down to get through.

“But also, sometimes those things are there for a reason. We have institutions and traditions, They can be very frustrating, but they’re not just a bug. They’re a feature of any modern democracy. You need to have brakes on untrammelled power.

“And I think if you look at a lot of his intellectual heroes, they weren’t operating in democracies, they were people who took a lot of power into themselves..

“People like [German Chancellor] Bismarck, people like Lenin. I’m not saying he agrees with what any of these people did, in terms of their beliefs, but he was always very taken by the fact that they were able to kind of smash through an archaic system.”

Soon after he entered Downing Street this summer, Cummings wanted to show he meant business about shaking up Whitehall. He swiftly centralised the special adviser network, famously calling a 7.55am Monday meeting with just a few hours’ notice the night before.

One of those present at that first meeting recalls that many of the young advisers hung back from approaching him. “No one wanted to get near him…people genuinely looked scared of him”.

“There’s the inner circle of Vote Leave types in No.10 but amongst others, while there’s respect for his strategic mind, there isn’t for his style. A lot of people feel very sore. And there’s a growing ex-spad network pissed off, not surprisingly since many were blocked by him.”

One insider says Cummings now “wastes so much time on HR”, including things like pay rises and contracts. Of course, it was his desire to personally intervene among special advisers that led to his now infamous sacking of Sonia Khan, Sajid Javid’s media adviser.

As HuffPost revealed at the time, she was summarily dismissed and escorted off the premises by an armed police officer. “It was like a public execution, that’s what really upset people,” one aide recalls.

Javid became the first cabinet minister to officially complain about Cummings when he met Johnson the next day. Her case is still being resolved but it looks likely she will emerge with no discredit and with a likely pay-off.

In a lecture in 2014 while he was out of government, Cummings had actually warned of his irritation with usual HR processes in Whitehall, especially for civil servants.

“Almost no one is ever fired,” he said. “Time after time after time, I would be in the [Education] department and on a TV screen it would say ‘Latest Gove disaster, Gove botches X’, and I would look through the glass screen and you would see the official responsible for it the lift, pottering home at 3.30 in the afternoon, doesn’t care. Why not? Because failure is normal, it is not something to be avoided.”

“Between flexible hours, compressed hours and a culture that says it’s perfectly acceptable to go on holiday the day before an announcement you’ve been working on for the last six months, it is very hard to get everyone in the same room. So we just had to ban announcements on Monday, because we knew it would all just fall apart.”

There are mixed messages too. At the very first special adviser meeting, Cummings told staff that if they or their minister felt No.10 was making a mistake, they should tell him. Feedback was to be encouraged. But since then, several feel any department or minister which doesn’t precisely follow his orders will feel the wrath of Downing Street.

Still, Cummings’ admirers say his big asset is he doesn’t buckle when things get tough.

At the most recent spad meetings last week, he appeared to relish the coming week as the government faced its Supreme Court verdict and as more election-focused policy announcements were lined up, one source said.

Cummings even joked on Friday to colleagues that if the court decision went against the government, it could use executive power to once again prorogue parliament.

The Cameron memoir publicity has already been ‘priced in’ too, with Johnson’s chief adviser believing the ex-PM’s re-emergence will remind voters why they voted Leave in the first place.

Cummings himself last week gave a rare public comment when the media doorstepped him outside his house “You guys should get outside London and go to talk to people who are not rich ‘Remainers’.”

It’s perhaps not Remainers but Brexiteers who could be most in his sights in coming weeks, if Johnson does push ahead with an amended deal with Brussels.

Cummings has never held back from his contempt for the European Research Group (ERG) of hardline Tory MPs. He famously described former Brexit secretary David Davis as “thick as mince, lazy as a toad and vain as Narcissus”.

Davis has now gently hit back at that trio of criticism with a three-pronged attack of his own. “It wasn’t so clever for various people in Number 10 to do things which are either unwise or careless or even arrogant,” he tells me.

“‘We’re going to have an election on this day, we’re going to do this.’. why would you do that? What’s what’s the point of that sort of briefing, except to make some spad feel important? Broadly speaking Boris has been right, but I think he’s had some problems visited on him by an over talkative number 10 over the summer in particular.”

Davis refuses to comment directly about Cummings, but his views are clear. “He and I are not friends. So I’ll probably pass on the invitation to continue to criticise him.

“One of the minuses I’m afraid has been the fact that Number 10 has in effect itself provoked all sorts of unnecessary actions, whether it’s about the 21 [rebels with the whip withdrawn], or whether it’s about the choosing of the prorogation. All of these things have been made worse by Number 10’s briefing.”

Yet for those who have worked closely with Cummings, there is a sense that it will all be worth it. If Johnson’s leadership bid had not imploded in 2016, the plan had been for Cummings to go with him to No.10 and immediately deliver on their £350m a week pledge for the NHS.

Like Johnson, he shares a sense of impatience that the last three years have nearly killed Brexit.

“What’s not sufficiently appreciated is Brexit is the vindication of years of work, ever since Dom was in Business for Sterling [the 1999 group opposed to UK membership of the euro],” one insider says.

“To see it all thrown away in the way the May government looked like it was doing, in an incompetent, dilatory, indolent way, this was a big thing for him and everyone who worked on Vote Leave.

“Having seen Brexit handed to Davis and Liam Fox, to grab the chance to see it through was irresistible.”

Stuart Wheeler, the millionaire spread betting boss and Brexiteer, was one of those who helped Cummings get involved in the referendum.

He remains a huge admirer, so much so that a plan has been mooted for the No.10 chief to ‘interview’ the financier at an event to launch his new autobiography later this month. It’s unclear if the plan will go ahead.

But for Tory MPs, ministers and even in some in No.10, the big question is how long Cummings will stick around, and whether his ‘scorched earth’ policy (as described by ex minister turned Lib Dem MP Sam Gyimah) is sustainable.

“For many of us the most interesting question is not what Boris is going to do next. It’s what’s Dom’s next move?”, says a former colleague.

One government insider says that the way Cummings himself talks about his future has changed. Initially he suggested he wouldn’t stay after Brexit was delivered, then he hinted he could be in Whitehall for the long term.

More recently, some think his real aim is to mastermind the Johnson general election campaign. The lure of winning, and winning decisively, is what tempts him.

But there is one big problem, according to some in the party: Sir Lynton Crosby wants to resume his election-winning partnership with Johnson (they twice won the London mayoralty together).

At present there is understood to be a stand-off between him and the former Vote Leave chief over who should be top dog in the snap election campaign.

One former Cabinet minister says the case against Cummings is obvious: “He didn’t win the referendum, he tainted the referendum. Turkey migrants? £350m on a bus? All him.”

Others say Cummings, who has a health condition whose treatment has been postponed because of his No.10 role, could step aside while offering tailored advice when needed. But one Tory source says Cummings “would love” the chance to be in charge of the campaign.

Some Tory MPs privately hope that Cummings could end up like Steve Bannon, exiled from power after overstepping his role.

What worries them most is his evident lack of affection for the party. In his final, personal blog before entering government this summer, Cummings wrote that a second EU referendum was “quite possible” in 2020.

And a new referendum “might be the ideal launchpad for a completely new sort of entity, not least because if it happens the Conservative Party may well not exist in any meaningful sense (whether there is or isn’t another referendum)”, he warned.

Whether Johnson’s government exists in any meaningful sense in coming weeks may well come down to what Dominic McKenzie Cummings does next.