12 Years A Slave star Chiwetel Ejiofor has revealed he had no reservations about the harrowing scenes in the film.
The British actor, 36, is tortured in his portrayal of Solomon Northup, a free black man who was kidnapped and sold into slavery in 1841, in Steve McQueen's film.
"There was no other way to tell the story. I have to just slip down the rabbit hole and see what happens," he said ahead of the film's UK screening at the BFI London Film Festival.
Ejiofor continued: "I was aware of Steve and his films so I knew those places you'd have to go to and that's what I wanted - to tell the story. You can't tell a story about slavery without showing those scenes."
Director McQueen said the scenes were essential.
"The book is pretty extreme. Either I make the film about slavery or I'm not," he said.
"And if you're making a film about slavery, you have to understand how people are incarcerated over the years with physical and emotional torture," he added.
McQueen praised his leading man, saying he was his first and only choice for the role.
"The one actor I knew who could play him was Chiwetel. He brought a stature, the class, the dignity to him," he explained.
"Chiwetel's just a great actor and brought a sort of stature to him that translates on screen. That's why Chiwetel is one in a million."
The British-born filmmaker, whose previous films were Shame and Hunger, said he wants the subject of slavery to be a talking point.
"There is sometimes a huge hole in people's minds and they don't want to think about it," he said.
"You must remember I, as an individual, am here because members of my family went through slavery. Fact. That's all to say really."
12 Years A Slave opens in cinemas on January 24, 2014.