To some, he's a strategic genius. Others call him a mayhem-loving anarchist.
Everyone seems to have an opinion about Dominic Cummings. British Prime Minister Boris Johnson's most powerful aide — dubbed "Boris' brain" by some — is an enigmatic backstage operator who shuns media attention, yet has been played onscreen by "Sherlock" star Benedict Cumberbatch.
Since taking office two months ago, Johnson has made a series of bold moves: Promising Brexit "do or die," dealing ruthlessly with party rebels and controversially suspending Parliament. Many see Cummings' hand at work in the strategy, which has left Westminster shaken and the governing Conservatives divided.
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Former Conservative Prime Minister John Major — not a fan — called Cummings a "political anarchist, who cares not a fig for the future of the party I have served."
"We have seen over-mighty advisers before. It is a familiar script. It always ends badly," Major told a business dinner Sept. 5. "I offer the prime minister some friendly advice: get rid of these advisers before they poison the political atmosphere beyond repair. And do it quickly."
Cummings, 47, is used to being a divisive figure.
He grew up in the northern England city of Durham, where — unfashionably for a northern kid in the 1980s — he was a fan of right-wing Prime Minister Margaret Thatcher.
He studied history at Oxford University, where classmate Lebby Eyres remembered him in the Daily Telegraph as "a loner" with "a love of argumentative conversation," keen on chess and the geopolitics board game Risk.
After university he spent three years in Russia, where he was involved in a failed attempt to set up an airline, before getting involved in British politics. He worked for Business for Sterling, a group that opposed Britain joining the euro single currency, advised then-Conservative Party leader Iain Duncan Smith and worked for the Department for Education amid a contentious attempt to radically reshape the school curriculum.
Cummings likes big ideas, and for years has explored them in a series of long blogposts discussing everything from game theory to the ancient Chinese general Sun Tzu. He is a particular fan of the military strategy known as the "OODA loop"— "Observe-orient-decide-act" — as a way of deceiving and defeating opposition.
In late 2015, Cummings was hired to help run the "leave" campaign in the following year's European Union membership referendum. He later said that at the beginning, the Vote Leave campaign amounted to "me and a bike and an iPhone."
He is credited with coming up with the campaign's highly effective slogan "Take back control," but has been accused of crafting misleading messages such as the inaccurate claim — emblazoned on a big red bus — that the U.K. sends the EU 350 million pounds a week that could be used instead to buttress the National Health Service after Brexit.
Crucially, he hired Canadian data-science firm AggregateIQ — which had links to Cambridge Analytica — to find and connect with voters the other side was overlooking during the pitched referendum campaign.
Debate has raged ever since about the role of targeted ads and social media data-harvesting in the referendum's outcome. Vote Leave has been investigated by Britain's election watchdog, and fined for overspending, and Cummings was found to be in contempt of Parliament earlier this year for refusing to give evidence to a committee of lawmakers investigating "fake news."
The saga was dramatized in the TV movie "Brexit: The Uncivil War," with Cumberbatch playing Cummings.
Cummings' appointment as a top Downing Street adviser after Johnson became prime minister in July took many people by surprise. He has long been scathing about civil service bureaucracy, and according to former Foreign Office Minister Alistair Burt, "he despises politicians."
Some argue that Cummings is a guerrilla-style campaigner, unsuited to the day-to-day operations of government. But Johnson has structured his premiership as an insurgency with one overriding goal: take Britain out of the EU on Oct. 31, deal or no deal.
He has met stiff resistance. Parliament tied the prime minister's hands with a law designed to block a no-deal Brexit on Oct. 31, prevented Johnson from calling a snap election and ordered him to release the government's stark forecast of the impact of a no-deal exit.
In turn, the prime minister expelled 21 Conservative lawmakers who voted with the opposition from the party parliamentary group, then suspended Parliament until Oct. 14, little more than two weeks before Britain is due to leave the EU.
Opponents have challenged Parliament's suspension, with the Supreme Court on Tuesday due to consider whether it should be reversed. Meanwhile, Brexit day is less than seven weeks away, and the new divorce deal Johnson says he aims to seal with the EU has proved elusive.
Critics say Cummings has overreached himself. Others suspect he probably has new tricks up his sleeve.
Sam Freedman, who worked with Cummings at the Department for Education, tweeted recently that "Cummings isn't the omniscient ubermensch that some of the Tory spin is making him out to be. He does however have an intuitive understanding of true populism which is very rare in Westminster. I fear some of his opponents are underestimating him again."
Cummings says little, at least in public. On Sept. 10, he told reporters who staked out his home that "you guys should get out of London, go and talk to people who are not rich remainers."
One reporter shouted: Will Britain leave the EU on time?
"Sure," he said.