Operation Wedlock was a 20-year investigation by MI5 looking for a suspected Russian double-agent within MI6. Operation Wedlock ended in 2015 as "inconclusive". According to

Gordon Corera Gordon Corera (born 1974) is a British author and journalist. He was the BBC's Security Correspondent and specialised in computer technology from 2004 to November 2024, he now co-presents the podcast The Rest is Classified (which is about the ...

in his book ''The Spy in the Archive: How One Man Tried to Kill the KGB'', the basis for the investigation was that the CIA alleged that an unknown MI6 officer was "turned by Moscow" and supported Russia's interests by sending to Russia secrets from MI6.

References

{{Reflist United Kingdom intelligence operations Soviet Union–United Kingdom relations Clandestine operations