Angelina Jolie has revealed she was really nervous about playing Mariane Pearl in new film A Mighty Heart because she’s friends with Mariane in real life.

In a joint interview with Mariane for Glamour magazine, Angelina said recently: “I was so nervous! I mean, it’s like you’re in a roomful of your closest friends and somebody says, ‘Why don’t you get up and imitate the friend to your left?’ Nobody would want to do that, ever!”

The two women became friends after Mariane read an interview with Angelina in a magazine a few years ago: “I read an interview with Angie in a magazine, about her and Maddox and her life as a single mom. And I thought, this woman could be my friend… I’d never experienced anything like that before in my life. It was something in her tone, in the answers that she gave. I felt also that Maddox and [my son] Adam could be good friends.”

Angelina added: “Her instincts were right - we did have so much in common. And all the kids are great friends now. Zahara is madly in love with Adam.”

But that made it all the harder for Angelina to play Mariane on screen, particularly in the scene where the character is told of husband Daniel Pearl’s death at the hands of militants in Pakistan. She said: “I had to express the worst time in her life and the moment when she received the worst information of her life. It became the worst acting day of my life and really, the hardest thing I’ve ever done.”

Mariane wrote a book about Daniel’s life and murder (A Mighty Heart: The Brave Life and Death of My Husband, Daniel Pearl) and was approached by a number of production company’s - including Brad Pitt’s Plan B - over the film rights: To be honest, I wasn’t even sure I wanted to do a movie… Everybody was using terrorism for their own political agenda at that time, and really, this is a story about Danny. But when I met Brad - well, out of all the studios, he was the only one who had actually read the book.”

She added that she thinks Daniel would be proud of how the film turned out: “He’s the person I did it for. If it were just for me, I wouldn’t have done a movie at all. But without the book and movie, he would’ve been known more for the way he died than the way he lived. I couldn’t accept that.”