During the film's London premiere, sisters Zindzi Mandela and Zenani Mandela, who were in the audience, were notified by cell phone of the news that their father Nelson Mandela had just died. When asked whether they'd like the screening to be postponed, they insisted that the premiere go ahead as planned. The sad news, however, was not shared with the rest of the attendees who sat through the screening unaware of Mandela's death. It wasn't until after the credits rolled at the end of the film that co-producer Anant Singh took the stage to break the news to the audience. The auditorium lapsed into a 2-minute silence as a gesture of respect.
The film was in development for many years, initially with Morgan Freeman attached to play Nelson Mandela. These plans were scuppered when Freeman chose to play Mandela in Clint Eastwood's Invictus (2009).
In order to prepare for the role, the actor Idris Elba spent a night in the real Robben Island prison, locked in a cell next to the one where Nelson Mandela was jailed for 18 years.
His trial in 1963 featured in the film was not his only major defense against the state. Between December 5, 1956 and March 29, 1961, he and 29 other freedom fighters either in support of or members of the African National Congress were tried for treason against the government. The trial lasted for nearly four and a half years, and after nearly 12000 documents seized by government officials were reviewed, he and the others were found not guilty. These events are well documented in Mandela's autobiography off of which this film is based between chapters 23 and 39.
Naomie Harris has said that portraying Winnie Mandela was the most difficult challenge of her career in that she had to inhabit up to 7 different complex characters that comprised the woman.