In the Dominic Cooke-directed film, the Emmy winner plays Greville Wynne, a British businessman who was recruited as a spy by MI6 during the Cold War.
Wynne formed a partnership with a soviet military officer that helped prevent nuclear war and put an end to the Cuban Missile Crisis.
Cumberbatch, 44, had to undergo a dramatic weight loss to play his character who was eventually caught by the Russians and starved while in prison for 18 months.
“We stop filming for three months to lose the weight and for me to do it with lots of cold water, swimming and exercise, and healthy foods,” he told Fox News while promoting the film. “I felt that physical vulnerability… mental instability, as well, a little bit. And that was just a clue to what the man himself must’ve suffered for months or years.”
Cumberbatch added how he always feels a deep responsibility portraying a real person in a film.
“You do feel a responsibility to bring a story to light that a lot of people either forgotten or never heard of, especially around an era of history that is fairly well known in the shape of the Cuban Missile Crisis,” he added.
The “Dr. Strange” star expanded, “This is an extraordinary character, a humble man from a very humble beginning, an ordinary man an everyman hero who has to do something quite extraordinary and not only for his country and his family.”
FOX’s Liza Aristizabal contributed to this report.