Michał Franciszek Goleniewski, also known as 'SNIPER' and 'LAVINIA' (16 August 1922 – 12 July 1993), was an officer in the Polish People's Republic's Ministry of Public Security, deputy head of military counterintelligence GZI WP, later head of the Polish Intelligence technical and scientific section, and in the 1950s a spy for the Soviet government.

In 1959 he became a "triple agent", giving Polish and Soviet secrets to the Central Intelligence Agency that directly exposed George Blake and Harry Houghton.

[1] In early 1959, Goleniewski became a triple-agent, anonymously sending Polish and Soviet secrets addressed to the US Federal Bureau of Investigation (FBI) by letter.

According to Tim Tate, author of the 2021 book The Spy Who Was Left Out in the Cold, Goleniewski's motive, unlike most defectors who sought a better life outside the Soviet Union, was that he "realised that the communist system was wrong.

[4] The mole himself (who later turned out to be George Blake) heard the news that the CIA had a top-level informant in Poland, and sent word back to the KGB, who passed it to the UB.

[5] He also provided information that led to the arrests of American diplomat Irvin C. Scarbeck, Swedish Air Force officer Stig Wennerström, as well as Heinz Felfe and Hans Clemens, who penetrated the West German BND for the KGB.

[7] He defected to the United States in January 1961, which led to the imprisonment of Soviet agents in Britain including the Portland spy ring and George Blake.

This caused Goleniewski much financial and emotional distress, and he lost his grip on reality, becoming paranoid, and ultimately completely insane, according to Tate.

[3] Goleniewski later made the claim that he was Tsarevich Alexei Nikolaevich, who is now known to have been killed with his family by Bolsheviks at Ekaterinburg, Russia on 17 July 1918.

[8] As author Guy Richards (one of Goleniewski's supporters) has pointed out, he was not the first Tsarevich Alexei claimant to emerge from Poland; several decades earlier, in 1927, a pretender named Eugene Nicolaievich Ivanoff had appeared from the same part of that country and generated a brief flurry of publicity in Europe and North America.

His claims are detailed in the books Lost Fortune of the Tsars by William Clarke, and Hunt for the Czar by Guy Richards.