Was sent to London under the guise of heading up a trade delegation, but was actually supposed to setup and oversee a spy network. Had attempted to make contact with the West previously but had been unsuccessful. Before he left for London he gave a package to Greville Wynne, a British businessman, who delivered it to the British Embassy in Moscow. Indicating that he wanted to provide information to the Western powers (Britain and the U.S), Penkovsky was met with a receptive audience. He was debriefed by a joint MI6-CIA contingent and Penkovsky warned that the Soviet Union would likely send missiles to Cuba. The level of detail that Penkovsky provided as well as the nature of his disclosures shocked the incredulous Western agents.

Was made a double agent, pretending to pass classified information to the Soviet Union while actually passing it to the U.S., and Britain. Given the codenames "hero" buy the U.S. and "Yoga" by Britain.

While most information was gained during extensive debriefings (he would ultimately spend more than 140 hours being debriefed), Penkovsky also passed information to U.S. agents, including Wynne and also Janet Chisholm, a former MI6 secretary and wife of a MI6 intelligence officer.

Provided vital information about Soviet plans for East Berlin and evidence that the United States had a clear advantage in the number and sophistication of missile weaponry.

KGB officials became aware that many of their secrets were being received by the West. After an investigation, their focus centered on Penkovsky. Although he was monitored he was nit immediately arrested. Finally, on October 22, 1962, Penkovsky was arrested by KGB agents. Wynne was arrested a few weeks later and was subsequently sentenced to three years in prison and five years in a labor camp. Penkovsky, on the other hand, was tried in a highly publicized media circus. He was convicted and sentenced to death, executed in May 1963.

Penkovsky was one of the most valuable double agents ever to work with the West. Because of his efforts, more than 300 KGB and GRU agents were recalled back to the Soviet Union and the head of the GRU, Ivan Serov, was fired and reported killed himself.