Zenani and Zindzi Mandela attended the premiere and learned of their father's death during the screening. Though the pair left the Odeon Leicester Square theater, they asked that the film play to the end uninterrupted, according to a statement from the Nelson Mandela Foundation.
Zindzi Mandela had spoken about her father's health on the film's red carpet, saying that he was "fine."
"He's just a typical 95-year-old who is frail," she added.
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"It was extremely sad and upsetting news," William told the press while leaving the theater. "We were just reminded what an extraordinary and inspiring man Nelson Mandela was. My thoughts and prayers are with him and his family."
Actor Idris Elba, who portrayed Mandela in the film, echoed the sentiment.
"We have lost one of the greatest human beings to have walked this earth, I only feel honored to be associated with him," he told reporters.
– The Associated Press contributed to this report.
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