The mystery of who was behind the Nord Stream pipeline blasts in the Baltic last year appears to have defied the world’s most sophisticated intelligence services. Now the case may have been cracked — not with the help of any government agency but by a group of Nordic journalists united by an enjoyment of vodka and puzzles.

The seven journalists from Denmark, Sweden, Finland and Norway published detailed evidence last week of Russian vessels loitering near the site of the explosions. Their findings were aired in a podcast chronicling tense meetings with mysterious contacts and cat-and-mouse adventures on the high seas.

Investigations into the seabed sabotage continue and several theories have been suggested. But crucial details unearthed by the Scandinavian journalistic consortium add to growing evidence linking the Russian navy to the attack. The Russians may also have mined other seabed infrastructure, including in British waters, according to experts.

The Scandinavian journalists who uncovered information that defied the world’s most sophisticated intelligence services.

To find out more about the Scandi sleuths and how they made their discovery, I call Frederik Ledegaard, 29, the youngest member of the consortium. He is a history graduate and Russian post-punk rock enthusiast turned investigative journalist at DR, the Danish equivalent of the BBC.

“We got together just over a year ago, spurred by the Russian invasion of Ukraine,” he tells me. “We wanted to investigate how Russia was conducting hybrid warfare in Nordic countries.”

Ledegaard, who lives in Copenhagen, is a self-confessed “nerd” whose “passion and hobby” — like the internet sleuths at Netherlands-based investigative journalist group Bellingcat — is open-source intelligence gathering and “all things to do with geolocation”.

He says his DR colleagues, Niels Fastrup and Lisbeth Quass, came up with the idea of a Scandinavia-wide investigative collaboration, reaching out to state broadcasters in Sweden, Norway and Finland for help chronicling Russian incursions. One of the team lives in the Norwegian Arctic Circle where Russia is accused of severing undersea cables.

The investigation led Fastrup into the Baltic aboard a rubber dinghy in pursuit of a Russian “ghost ship”, supposedly a scientific research vessel. Visible on deck were men in beige body armor holding automatic rifles. “I decided to reverse very slowly away from there,” says Fastrup.

Another episode takes him to the English countryside to meet a source identified only as James. To relieve the boredom of retirement, this mysterious figure had been eavesdropping on top-secret Russian naval communications — this had been his speciality, it turns out, when employed years before as a Royal Navy officer.

“I spent 30 years beneath the sea and on it,” says James in the podcast. “I was conducting research against our traditional adversary, the Russian navy, and gained a good deal of experience against that target.”

But how did he manage to intercept Russian military messages from his sitting room?

Visible on deck were men in beige body armor holding automatic rifles.

“I was really skeptical at first,” says Falstrup. He was also slightly anxious, having been contacted by James out of the blue. But he began to think James might be telling the truth when invited to put on a pair of headphones: “I could hear two Russian men speaking together.”

Using only the internet and open-source intelligence, the British source claimed to have built a database on Russian “ship movements” and activity as a way of amusing himself during lockdown.

Sibiryakov, the Russian “research” ship with a submarine on board.

“It became apparent that if you knew where to look, a good deal of information could be readily gleaned from those sources,” says James in the podcast.

This helped the Scandinavian team to determine that various Russian ships, including the Sibiryakov, a large research vessel with a submarine on board, another submarine ship called the SS750 and a tugboat equipped with a large crane, had visited an area near the explosion sites three times between June 6 and September 22, four days before the attacks.

The ships had sailed from naval bases in St. Petersburg and Kaliningrad in June and September. But halfway to the site of the blasts they had gone “dark”, meaning they had switched off their position-signalling transponders. Their location then could only be determined by intercepted radio communications.

The journalists decided to check the location of the vessels on the dates provided by James against historic satellite imagery of the blast sites. These confirmed the presence of the Sibiryakov and other “ghost ships” that had switched-off transponders.

The blasts deep under the Baltic severely damaged the Nord Stream 1 and Nord Stream 2 pipelines, halting delivery of natural gas from Russia to Europe. The incident prompted months of speculation. The Kremlin denied involvement — why would it blow up its own pipes? — and instead pointed a finger at Britain, which also denied involvement.

Then it was claimed in an article by Seymour Hersh, the veteran American investigative journalist, that a special US military operation had taken out the pipes. The story relied solely on one unidentified source. America denied it.

But how did he manage to intercept Russian military messages from his sitting room?

Another theory had it that non-government pro-Ukrainian operatives were responsible. This was based on reports that a group of men had rented a yacht from which they had planted explosives — traces of explosive were found in the cabin. Kyiv denied any role.

According to evidence gathered by the Scandinavian team, Russia has long been mapping critical infrastructure on the seabed, including wind turbines off the northeastern British coast, in readiness for a wider war in which it may want to engage in sabotage.

An aerial photo released by the Danish Ministry of Defense immediately after the explosions last year.

“There’s a military program in Russia focusing on seabed warfare, we see from the way Russian vessels move in northern waters they are specifically interested in critical infrastructure, pipelines, cables and wind turbines,” says Ledegaard, adding: “We’ve only been able to lay bare the tip of the iceberg.”

So did Russia blow up the pipelines? “We don’t conclude anything,” he replies. “We put forward some data which could be related to the explosions, but we don’t know, we don’t go into that.” James, the British informant, adds in the podcast: “At the end of the day, we don’t know if it’s the smoking gun.”

Another important piece of evidence, though, came from Denmark’s Defence Command which last month confirmed a report that a Danish patrol boat called Nymfen had taken 26 photos of a Russian submarine-rescue ship in the area of the explosions.

The Scandinavian team, for its part, has kept busy. Besides Cold Front, their podcast, they have produced Putin’s Hidden War, a television documentary — and more exclusives are imminent, promises Ledegaard.

They intend to celebrate their success. “We have an agreement to meet in the near future to drink a glass of vodka,” he says. “We’re unsure, though, if it should be Russian or Scandinavian. There are some good local brands.”

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