Eliot Higgins taps on his laptop, peering at the screen. It is a few days before Russia’s invasion of Ukraine. We are in his sitting room at the end of a cul-de-sac near Leicester — but we’re looking at an area in eastern Ukraine. “Bloody clouds,” says the 43-year-old founder of the investigative journalism group Bellingcat, staring into a white swirl on the screen. “Clouds are the biggest enemy of satellite imagery.”

Russia beware: the world’s most celebrated Internet sleuth is watching. Armed with a bulging budget and new technical wizardry, he is logging growing evidence of war atrocities allegedly committed by Russian troops.

“It’s the way the Russian military fights,” says Higgins, complaining of President Putin’s “total disregard” for civilian casualties. “We saw the same thing in Syria.” Russian shelling razed towns as part of Putin’s intervention to prop up the dictator Bashar al-Assad in 2015.

One of the Russian nationals, caught on security footage, connected to the Salisbury Novichok attack and Amesbury investigation.

In Ukraine, Higgins says, he has proof of cluster munitions being used by Russia in civilian areas. It will go into an ever-expanding archive of evidence he hopes will be used against the country in international courts. He has pioneered the practice of harvesting what he calls open-source material: photographs, videos and other information freely available on the Internet that can be used to investigate international criminality.

The bearded figure in a hoodie and burgundy jeans is already the scourge of the Kremlin for exposing its team of bungling poisoners. He publicly identified the two agents sent to Salisbury in 2018 to kill the defector Sergei Skripal by smearing Novichok, a lethal nerve agent, on his door handle (they failed); and unmasked others who sprayed the same poison on the underpants of Alexei Navalny, Putin’s chief critic. Navalny spent 18 days in a coma and was then jailed.

Another of Bellingcat’s coups was to identify the Russian vehicle that fired the missile that brought down a Malaysian civilian airliner over Ukraine in 2014, killing 298 people. A Dutch court is prosecuting three Russians and a Ukrainian, who are about to be sentenced in absentia.

Just before the invasion, Higgins was busy exposing bogus social media posts that painted Ukrainians as the aggressors to justify Russia’s intervention. “What’s particularly surprised me with the disinformation from the Russian side is how poor quality it is — and how we’ve managed to quickly debunk so many serious allegations, including confirming that videos of supposed Ukrainian attacks are fabrications,” he says. “After so many years of calling out Russian fakes, I honestly thought they’d have learnt something, but so far it appears they’ve regressed.”

The site of the 2014 crash of a Malaysia Airlines Boeing 777 flight from Amsterdam to Kuala Lumpur, near the Ukrainian-Russian border.

Higgins took the Bellingcat name from a medieval fable in which mice decide to put a bell on a cat’s neck as an early-warning system to avoid being eaten. What started as a crowdfunded one-man show is now a thriving enterprise employing 30, with a headquarters in the Netherlands and an annual budget of about $2.6 million. It holds training workshops, which account for 30 percent of its income; half comes from large funders, including America’s National Endowment for Democracy; and the rest is individual donations. But although tracking down Russian state killers and documenting war crimes may sound glamorous, only the obsessive need apply.

He has pioneered the practice of harvesting what he calls open-source material: photographs, videos and other information freely available on the Internet that can be used to investigate international criminality.

“That’s the nature of open-source investigations,” says Higgins. “You need that obsessive energy. Often in these cases there’s just a mass of information. After the Washington violence last January, when rioters attacked Congress, I spent weeks looking through several hundred videos trying to figure out exactly where they were filmed and putting them into a timeline.”

Moscow dismisses Higgins as part of a Western intelligence conspiracy, which makes him laugh: “I’m not organized enough to be part of any conspiracy.” He understands that Putin may have bigger things on his mind, but in case of trouble he has been given a number to call at the West Midlands anti-terrorism police. “If anyone calls 999 and mentions my house, there’s notes saying, ‘Don’t touch the door handle’, and stuff like that,” Higgins says with a grin. “The police take it very seriously.”

Born in Shrewsbury, he was painfully shy as a youth, a keen player of video games and the tabletop fantasy game Warhammer. He hated going out — and still does, though not to the same extent. I ask how he managed to meet Nuray, his Turkish wife, with whom he has two young children. “On the Internet — where else?”

Higgins, center, addresses a press conference on findings into the Malaysia Airlines Flight MH17 downing.

Higgins dropped out of a media studies course to do a variety of administrative jobs. He attempted a conventional journalism career but was rejected, much to their regret now, by the BBC and ITN. Perhaps through paternal influence — his father was an RAF engineer — he had developed an interest in military matters and began examining conflicts in the Middle East, studying videos posted by citizens caught up in the conflict.

The explosion of social media and smartphones made it possible to see what was going on in distant war zones, and his breakthrough came when he identified weapons from Croatia in a video posted by a jihadist group in Syria. The story he wrote on his blog was picked up by The New York Times on its front page. He went on to document the Syrian regime’s use of chemical weapons.

Bellingcat is collecting videos showing troop movements in Ukraine: “If there’s a war crime, we’ll want to know where these different units were when it occurred. There have been cases where from one video we’ve managed to get people prosecuted for murder.”

Matthew Campbell is a roving correspondent who, in more than 30 years at The Sunday Times of London, has covered numerous wars, natural disasters, and major political stories while serving as the paper’s bureau chief in Moscow in the early 1990s and, later, in Washington and Paris