Idris Elba, who plays the late Nelson Mandela in the biopic, Mandela: Long Walk To Freedom, revealed that he was initially hesitant to portray South Africa's first black president.

"When my agent called to offer me the role I said, are you trying to get through to Morgan [Freeman]?" Elba quipped at a recent New York City screening at the School of Visual Arts. "It was such a big and iconic role because I didn't feel I had the qualifications to play such a man. The honor of being asked was immense. The honor, to play this character the best way I can overwhelmed my trepidation."

Since Elba was aware of the fact that he does not physically resemble Mandela, he said he studied rare footage of the icon throughout the years to be able to get into character as best he could. He had also met the Nobel Peace Prize laureate, which helped him pick up his mannerisms.

"We were not doing the 'looky likey' thing," he said. "We owed it to the audience to be as close to anything else we could get."

Lack of physical resemblance aside, he instead, decided to focus on mimicking the late freedom fighter's voice. 

Elba shocked the screening audience when he said he had discovered from watching the footage of a young Mandela that he "spoke 100 miles an hour, with a high-pitched voice." He also revealed that Mandela stuttered. However, the actor and the film's director decided not to include Mandela's speech impediment in the movie.

"We thought it would be too much of a distraction," he explained.

The change in Mandela's voice over the years Elba believes, said a lot about what being imprisoned for 27 years had done to the anti-apartheid icon.

"The change in his voice tells you his journey, from when he was a young man. There was a real centering that happened to him [during his 27 years in prison]," he said. "He brought his voice down into his chest. He really took his time to speak, he was really thinking [in prison] the whole time."

"I wanted you to feel as if you were listening to him if he was speaking," he continued. "I listened to Mr. Mandela's tone for a long time and how he spoke English."

Aside from his thorough study, Elba said he felt confident after an interaction with the bold ex-wife of Mandela, Winnie Mandela.

"When we met she looked at me and said, 'my husband!' and she kissed me right on the lips," he revealed with laughter. "That was the end of my research."

Elba's portrayal even got a reaction from the former South African president himself. Producer Anant Singh, who started writing to Mandela in prison about the film 22 years ago, showed a scene of the movie to Mandela, and laughed as he remembered Mandela's first reaction.

"He saw Idris Elba as the old Mandela in the Mandela prosthetics and he says, 'Is that me?'" he recalled. "And it was very cute and he smiled and laughed, so it was very good."

Mandela: Long Walk To Freedom arrived in limited theaters on Nov. 29. It will be released in theaters nationwide on Christmas Day.

South African President Jacob Zuma announced on South African television that Nelson died at the age of 95 on Dec. 5.

Nelson became South Africa's first black president in 1994 after serving 27 years in prison. He was awarded the Nobel Peace Prize in 1993 and stepped down from ruling the country after five years in office.

Watch Elba's portrayal of Mandela in Mandela: Long Walk To Freedom below.