To the untrained eye, it may have just looked like a rock sitting next to a Moscow sidewalk, but to British spies prowling the Russian capital, it was actually an invaluable tool of spycraft, a fake stone with a hidden compartment for electronic equipment, according to a former British official.
It has been five years since the Russian security service, the FSB, claimed it had discovered a British espionage ring on Russian soil using the fake rock, but until now no British officials admitted the blown operation.
In a BBC documentary airing Thursday night, Jonathan Powell, then-chief of staff for former British Prime Minister Tony Blair, said "the spy rock was embarrassing" for the Brits, according to a BBC report.
"They had us bang to rights," Powell said. "Clearly they had known about it for some time."
In 2006, Russian television showed footage of the alleged spies using the rock to apparently transmitting files to and from electronic equipment hidden in the rock. In one instance, a man walked by the rock, slows down as he passes it, and then picks up the pace, according to the BBC. In the next shot, another man walks by and picks up the rock.
Powell told the BBC he believed the Russian government had held off making their discovery public for some time "for a political purpose." At the time, the Russian government had accused British intelligence of secretly funding pro-democracy and human rights non-governmental organizations in Russia.
Around the time the Russian report was shown in 2006, then-President Vladimir Putin introduced a new law that restricted NGOs from receiving funding from foreign governments.
At that time, Britain's ambassador to Russia, Tony Brenton, reportedly said all interactions between the British government and Russian organizations was "above board."
According to the Russian news outlet RT, the FSB denies the "spy rock scandal" was linked to the NGO funding controversy, but chose to leak the story to the press in 2006 only after the spy agency failed to discreetly settle the matter with the British government.
When asked for comment on this report, a spokesperson for the British Foreign Ministry told ABC News the office does not comment on "intelligence matters."
Mark Stout, a historian for the International Spy Museum and former intelligence analyst in the U.S. government, said such a method of "cover communications" is not uncommon for most major intelligence services.
"All the major services have technical staffs... in a lot of ways analogous to Q in James Bond, who are really good at this sort of thing and always looking for the latest, greatest ways to hide something in a place that no one would've ever imagined in a million years," Stout said.