The British actress spoke to The Huffington Post UK this week, before the death of the former South African president on Thursday.
"It was our greatest honour to show it to them," she told us, after revealing how "terrified" she was about taking on the part of the formidable activist and Mandela's ex wife, Winnie.
The Bond star explained there was an incredibly tense moment as she watched the biopic with the Mandela family for the first time.
"They were all at the South African premiere... there was silence throughout the film.
"I thought 'oh my gosh they don't like it' and then at the end one of Mandela's nieces was in my arms sobbing and Winnie's daughter was in tears," the Bond star said.
She added: "I realised they were processing it on a really profound level. It was not just a movie or a piece of history, it's their lives represented up there. If you capture it right, you force them to relive it and come to terms with things they hadn't come to terms with."
- The tweeters who still call Mandela 'terrorist'
- Nelson Mandela in memorable quotes
- Prince William and Kate attend Mandela film premiere, unaware of his death
- BLOG: The day I saw Mandela dance
- LOOK: How newspapers reacted to Mandela's death
- Queen remembers Mandela with 'great warmth'
- In pictures: A remarkable life
Also on HuffPost:
More:Nelson Mandela Naomie Harris Nelson Mandela's Family Nelson Mandela Dead The Long Walk To Freedom
HuffPost Entertainment is your one-stop shop for celebrity news, hilarious late-night bits, industry and awards coverage and more — sent right to your inbox six days a week. Learn more