The historical Cold War-era drama The Courier is based on the true story of Greville Wynne, a British businessman who became an unlikely MI6 agent in the early 1960s. Benedict Cumberbatch played Greville Wynne in The Courier alongside Merab Ninidze as Soviet intelligence officer Oleg Penkovsky, whose actions during the Cold War serve as the inspiration for the movie. In the early 1960s, Penkovsky, a high-ranking member of the Soviet's GRU agency, used American students to deliver a message to the United States about nuclear operations in the Soviet Union. In the letter, he also shared his desire to defect from the Soviet Union and agreed to pass along top-secret Soviet intelligence.

https://screenrant.com/courier-movie-true-story-wynne-mi6-soviets-explained/