In an interview to USA Today, he also spoke about meeting the real Lt. Colonel Stewart Couch and getting his accent right. Read more below:

A pivotal scene in “The Mauritanian” places the drama’s two biggest stars – Benedict Cumberbatch and Jodie Foster – head to head as opposing lawyers meeting unofficially. It’s a legal version of Al Pacino’s cop meeting Robert De Niro’s robber in “Heat,” set in the surreal location of a gift shop near Cuba’s notorious Guantanamo Bay Detention Camp.

It was Foster’s first scene and first day on the set in Cape Town, South Africa, which effectively stood in for the incongruent Caribbean paradise that surrounds Gitmo. But it was Cumberbatch who struggled as cameras rolled.

“I was getting sick in between takes,” Cumberbatch remembers, calling from a car somewhere outside of London. The 44-year-old “Doctor Strange” star thinks he was in the final stages of a terrible flu he picked up on the flight to South Africa. Or something. “I was really ill, I think it was just a really severe flu. But it was really nasty. I hadn’t been that ill for quite a long time. Like maybe once in my life. Horrible.”

In the pre-COVID era, Cumberbatch was intent on battling forth. “The Mauritanian” (in theaters Friday, on demand March 2) represented a five-year quest to bring Mohamedou Ould Slahi’s remarkable story to the screen.