On Boris Johnson's first day as the new UK prime minister, the British press started obsessing over a series of photographs that emerged out of 10, Downing Street. The object of their fascination was not their country's new leader — his trademark scruff of blonde hair carefully groomed for the occasion — but an unassuming figure lurking in the background.

This was Johnson's newly appointed senior adviser, Dominic Cummings (pictured above on the right). In a room of shirts and suits, Cummings signaled his outsider status by wearing a shapeless grey t-shirt, emblazoned with the words, Open A.I., the name of Elon Musk's artificial intelligence company.

Cummings' appointment has prompted a nationwide flashback to the 2016 Brexit referendum — the 47-year old led Vote Leave to victory and is famous for coining the campaign's potent "take back control" message. That reputation, as a disruptive force in the country's politics, has been carried forward to his new job. British newspaper, The Times, quoted an un-named minister comparing Cummings' communications style to "bringing a sub-machine gun to a knife fight," noting how he has been intimately involved in planning Johnson's £100-million (€110 million; $122 million) no-deal information campaign — reportedly the biggest government advertising effort since World War II — which the Conservatives launched this week.

Dominic Cummings is said to be pulling the strings in 10 Downing Street

But the advertising blitz is not the first piece of Conservative strategy linked to the adviser. Throughout the summer, the Conservative Party appeared to replicate the Facebook strategy used by Vote Leave during the referendum campaign. Under Cummings, who's been labeled as the "master of Brexit's dark arts," the campaign launched its own app which gamified the voting process and ran online data harvesting campaigns, spending more than £2.7 million on Facebook to find and target adverts at specific groups of people.

Read more: What role did Cambridge Analytica play in the Brexit vote?

In the digital dark

Martin Moore, author of Democracy Hacked, is wary about Cummings' methods and his lack of transparency. "Cummings has been clear that digital methods were essential to the Leave campaign yet we know very little about what those digital methods were," he says.

Read more: Facebook's Cambridge Analytica data scandal: What you need to know

But for others, Cummings approach to social media during the Brexit campaign was emblematic of a new era of online political advertising that started with Barack Obama's 2008 US presidential campaign — credited with being one of the first to successfully identify and mobilize voters using data analytics, micro-targeting and social media.

"Vote Leave used social media like all campaigns do," says Paul Staines, who writes for the political website, Guido Fawkes. "In my view, the reason you have all that [controversy] is because they weren't expected to win. It was the same magic that everyone saw Obama do in 2008 and thought it was brilliant. It's nothing particularly new."

Building up a database

On August 1, the Conservatives' page launched 841 Facebook adverts, publicizing Johnson's decision to hire 20,000 new police officers, "starting right now." The advert tells people to click the link, "to tell Boris where you want to see more police officers." That link opens a page on the Conservative Party website, asking them to enter their email address and their location.

Throughout the summer, the Tories appeared to replicate the Facebook strategy used by Vote Leave ahead of the referendum

"Any modern campaign will start by building up the biggest database possible, with as much relevant information as you can, including a person's contact details," says Moore, who is also a professor at King's College London. "Then they will run [computer] models through the data to figure out who to target based on marginal constituencies and who are the most susceptible voters."

Benedict Pringle, founder of the blog, Political Advertising, says the Conservatives' latest Facebook campaign is also designed to test which audiences respond best to certain messages.

"You can see on the ad library many identical versions of the same adverts," says Pringle. Facebook lets advertisers target users by location, gender, age range and political leaning, so identical adverts indicate that messaging is being tested against different demographics — to see who is most susceptible to adverts about police numbers, for example.

Read more: Brexit: Small English island reflects UK's island mentality

Producing vast numbers of adverts and testing them against different demographics is becoming the norm for digital campaigns. The Conservatives are not the only British political party to use Facebook this way and similar tactics have also been seen in Germany, Italy and the US. Talking about 2016's election, Donald Trump's digital director, Brad Parscale, told CBS: "(On an) average day (we would make) 50,000 to 60,000 ads, … changing language, words, colors, changing things because certain people like a green button better than a blue button, some people like the word 'donate' over 'contribute.'"

Preparing for a snap election?

The Tories spent more than £2.7 million on Facebook to find and target adverts at specific groups of people

Rachel Lavin works for Who Targets Me, a British organization advocating for more transparency. "Because [digital political advertising] is so powerful, the public should be aware of who's doing it, who's paying for it and what messages are being sent to different groups."

Pringle, of Political Advertising, agrees. "I'm a real advocate of the idea that political advertising can be a positive force in democracy. That's why I want to reform it." Last year, the blogger and advertising professional co-founded Reform Political Advertising, a campaign group that has suggested all paid-for political adverts — including online — should be listed in a central database which can be accessed by the public.

While regulation around political advertising has not been updated since the pre-Facebook era, Johnson's social media adverts confirm that digital campaigning is the new normal. With hints that the prime minister's team are preparing for a snap election, the UK could find out once more how well Cummings' tactics work.