Since his landslide election win in December, the British Prime Minister has attempted to frame his personal success as the moment Brits could confidently move on from Brexit and into a bright new future.

Yet despite Johnson's sunny optimism, a near-constant stream of darker, nastier messages has been seeping out of 10 Downing Street. And the finger of blame is being pointed at Johnson's most senior adviser, Dominic Cummings

Cummings is one of the most controversial figures in current British politics. Credited with masterminding the successful campaign to leave the European Union, Cummings has a reputation for being a control freak and a brutal disruptor who loathes convention and the political establishment in equal measure.

However, for all his apparent control-freakery, Cummings, according to some, is a man whose purest instincts are causing him to spiral out of control.

Since joining Johnson in Downing Street, Cummings has been at the center of the biggest arguments surrounding the British government. The most recent incident involved one of Cummings' subordinates, Andrew Sabisky, being forced to resign after it emerged that he had previously made comments in support of eugenics, and the relative intellects of black and white Americans.

The Metro newspaper, a free newspaper read by millions of commuters on their way to work all over the country, ran with the headline "Racist 'weirdo' quits No.10 job."

Dominic Cummings

That the word weirdo appears in quote marks is significant. It's a reference to an advertisement that Cummings posted on his personal blog earlier this year, inviting "weirdos and misfits" to apply to work in Downing Street. That's how Sabisky appears to have come to work for the Prime Minister. The government has refused to say whether he was properly vetted, or whether Cummings hired him without consulting anyone.

The Sabisky controversy followed months of "Classic Dom" moments, as the British media refers to his interventions. Highlights include firing the top adviser to a cabinet minister and then having her escorted from Downing Street by armed police; playing divide and conquer with the press by excluding out-of-favor journalists from government briefings; suggesting that the government is preparing for all-out war with the BBC; and putting the Prime Minister in the curious position of having to step in and defend the BBC from his own government.

Close allies of Cummings suggest that stories about him are blown out of proportion and that, rather than engaging in a communications battle and talking to journalists, Cummings spends the majority of his time dealing with policy and the day-to-day management of the Downing Street team.

But stories about the Prime Minister's most senior advisor are getting a lot of attention in the UK at the moment. And some government ministers and Conservative lawmakers are starting to lose patience. "There is a crushing loss of faith in Dom and his ability to deliver on this radical agenda," said one government minister, who rued Cummings' habit of drawing the limelight from otherwise positive stories.

CNN approached Downing Street and Cummings for comment on the claims made in this article, however they declined to directly address them.

The longer Cummings remains the most powerful person in Johnson's inner circle, the more likely that frustration is to infect the Prime Minister himself. "When Boris won the majority, there was a huge amount of goodwill from lots of us who were previously skeptical about his leadership. But we are still waiting to see what he does with that it," said one influential Conservative political figure.

That goodwill erodes every time Conservatives are forced to put out fires started by the man who is supposed to be driving their Prime Minister's agenda.

All of which leads to the question: why is Cummings still working for the Prime Minister?

"Boris has the power to rein him in if he wanted to. But at the moment clearly he feels that Cummings is doing what he wants him to do -- moving forward with a disruptive but productive program," says Tim Bale, Professor of Politics at Queen Mary University in London.

Cummings' allies point to the fact that despite his brutal style, he has delivered for the very same establishment Conservatives who find his approach to politics vulgar. "We might hear rumblings now and again, but he was vindicated when the Brexit deal happened in November. It was the same with the election," says a friend and former colleague. "As long as he keeps performing for Boris, the longer it remains worth it for Boris."

Boris Johnson (R) and Dominic Cummings at Downing Street in September.

And as long as Johnson continues to think having Cummings inside the tent is worth it, things are unlikely to change. "Dom's always been of the view that unless he's in complete control there is no point in him being in the job," says the Cummings ally.

Civil servants and other advisers who have worked with Cummings say his management style is to make it clear to as many people as possible that he is in total control. Once he has asserted his dominance, he attempts to expand his sphere of influence.

In Downing Street, he's done this by trying his best to erode the traditional relationship between cabinet ministers and their special advisers. Rather than be loyal to their bosses, advisers say Cummings demands they be loyal to him.

One former adviser to a cabinet minister said there was a drive to ensure that "Dom's people" were working for ministers deemed to be "rogue or disloyal."

And this isn't merely a power trip for Cummings. People who have worked with him explain that Cummings doesn't distrust people, he just doesn't trust them to make the correct decisions. Multiple sources told CNN that Cummings sincerely believes himself to be more intelligent than almost anyone he interacts with.

Johnson knew what he was letting himself in for. Allies of Cummings say that when he was offered the job, he made it clear to Johnson that if he was to build a loyalist court, then he wanted to be king. Special advisers believe that Johnson was happy to agree, because he didn't want to suffer the rebellions that ultimately brought down his predecessor, Theresa May.

Of course, Cummings is only powerful for as long as Johnson believes his aggressive style of politics is a net benefit. The real question is if and when Cummings tips over into being more costly than he's worth. "There is always a trade-off between having people feel like they have to get with the program or creating what some suggest is a climate of fear that impacts negatively on their loyalty and productively," says Bale, the politics professor.

Allies and enemies predict that this won't last forever. A government minister explained that Cummings' aggressive manner was "a bad look for a party with a reputation among some for being nasty."

And as one of his friends put it, "the more people who have run-ins with him, the more enemies he will have. I have half a feeling it [Cummings' demise] could end up being some sort of HR matter where he's clearly gone so overboard in terms of bullying. It could be his unusual hiring. Or it could be a bad decision."

If and when the end comes for Cummings, most believe it will be a self-inflicted wound. It will be because he cannot trust others to do things correctly, so he stretches himself too thin and makes a mistake. The image those who know him paint is one of a man who could easily blow himself up trying to fix his own boiler because he thinks the plumber is an idiot.

Until that moment, the most controversial man in British politics will continue to be the one of the most powerful men in British politics. And, as painful a pill this is to swallow, until Boris Johnson decides enough is enough, those tearing their hair out over Cummings' unusual approach to work will have to suck it up.