Chiwetel Ejiofor has defended the harrowing scenes of violence in his new film 12 Years a Slave.
The British actor plays a free black man from New York who was kidnapped and sold into slavery in 1841.
"As an actor you have to slip down the rabbit hole and see what happens because there was no other way of telling the story," Ejiofor said.
He was speaking before the film's European premiere at the BFI London Film Festival.
The historical drama, from British director Steve McQueen, is already considered a leading contender for the Oscars.
It contains several unflinching scenes in slaves are beaten and one where Ejiofor's character, Solomon Northup, is left hanging by a noose all day long, standing on tiptoes to stay alive.
Chiwetel Ejiofor: "I just had to trust in Steve"
"I knew that [Steve] would go to all the places that you'd have to go to and that's what I wanted to tell the story," Ejiofor told a press conference in London on Friday.
"It's a strange handicap if you can't talk about violence in a film about slavery. You are not going to do justice to any of the people involved.
"I read into the script that there were obviously going to be these struggles and I wanted to embrace that."
McQueen, whose films include Hunger and Shame, said that he had wanted to make a film about slavery and had been drawn to Solomon Northup's 1853 memoir, 12 Years a Slave.
"The book is pretty extreme," he said. "My responsibility is this: either I'm making a film about slavery or I'm not.
"If you make a film about slavery you have to understand why people were in bondage in this way for 400 years, through mental and physical torture."
The film has been receiving rave reviews ever since its first screening at the Telluride Film Festival in Colorado at the end of August.
Steve McQueen: "I made it my passion to make this
It won the People's Choice award at the Toronto International Film Festival last month, which can be an indicator of Oscar success.
The cast includes Michael Fassbender, Benedict Cumberbatch and Brad Pitt.
Earlier this week Fassbender was reported to have said he would not campaign for an Oscar nomination, despite being hotly tipped for his role as violent cotton plantation owner Edwin Epps.
"It's just a grind. And I'm not a politician. I'm an actor," the actor told GQ magazine.
Asked about Fassbender's comments, McQueen said: "He's an amazing artist. He's a force to be reckoned with."
"His campaign is on that screen," he added. "He's done his thing - that's it."
12 Years A Slave is out in the UK in January 2014.