The responsibility of portraying a woman she considers both a close friend and a remarkable human being weighed heavily on Angelina Jolie. To play Mariane Pearl, the extraordinary wife of the murdered journalist Daniel Pearl, in A Mighty Heart was, she says, both an honour and a huge challenge.

“I was very worried,” says Jolie. “I’ve never been so nervous about anything. I work very hard but I’m very casual about it, it doesn’t keep me up at night but this one did.

“The night before shooting I was tossing and turning and imagining everything that could possibly go wrong. I felt bad that I was even assuming that I could play this woman that I respected so much and I felt humbled to a point of being unable to move. But her faith in me really helped me so much.”

Jolie admits that when the finished film was finally screened for Mariane she was “incredibly nervous” worrying about her friend’s reaction.

And she was “hugely relieved” when Mariane told her privately that she was thrilled with director Michael Winterbottom’s film and indeed her performance and said so publicly after A Mighty Heart was given its world premier at this year’s Cannes Film Festival. “As soon as Mariane was fine then I was fine,” she says.

A Mighty Heart is based on Mariane’s book of the same name, which tells the story of how she met and fell in love with Daniel Pearl and of the dark days of his kidnap whilst he was investigating a story about the shoe bomber Richard Reid in Karachi.

Jolie’s partner, Brad Pitt, optioned the film rights to the book and the actress met Mariane socially at first, sharing a common bond as two young mothers who decided to take their children on a ‘play date.’

At the time Daniel was abducted Mariane was six months pregnant and now has a much adored five year old son, Adam. Jolie and Pitt have four children, Maddox, 6, Zahara, 2, Shiloh, 1, and three year old Pax.

“I knew Mariane a bit because we tried out play-dates, just as women and nothing to do with anything else,” explains Jolie. “Then separately Brad had bought the rights to the book after they had met a few times and she trusted him and then they got together and started to talk, it was like ‘OK, we’re going to make the movie, what do you think?’ and when it came to casting she mentioned me which was fantastic.”

Filming took place in Pakistan where Winterbottom shot in many of the locations where Daniel Pearl had met his contacts in the run up to his kidnap and in India where the production recreated, as faithfully as possible, the house in Karachi where the Pearls had been staying when he was abducted which later became the hub of the operation mounted to try and find him.

“I love those parts of the world and I love to travel. I much prefer that to a big fancy trailer and a Hollywood studio lot,” says Jolie. “So I was so grateful to be there and that’s what we all loved about Michael as a director and knew he would bring authenticity. And that was so important.

“And it was wonderful. We all lived in the house, we had no separate trailers and we never left to go to lunch or anything, in a separate building, we were in that house the whole time and that helped us to bond and to create the atmosphere that you see in the film.”

Jolie, 32, is one of the leading actresses working in cinema today and won an Oscar for her performance in Girl, Interrupted. Her impressive CV includes Beyond Borders, Mr and Mrs Smith, Tomb Raider, Alexander and The Good Shepherd.

She is a goodwill ambassador for the United Nations High Commissioner for Refugees and has travelled the world highlighting the plight of refugees.

This interview was conducted during the Cannes Film Festival where A Mighty Heart was given its world premier and received glowing reviews.

Q: It must be nice to be here with such a well-received film?
A: Yes it is. We’re so relieved. The reviews do make a difference and also we were able to send some good reviews to Danny’s parents and you think, thankfully we can tell them that it’s going well.’

Q: I would imagine that Daniel’s parents and Mariane were the toughest audience for you?
A: Absolutely. And once we knew that they were all right really it could have been the toughest reviews in the world and that wouldn’t have been good, but still as soon as Mariane was fine then I was fine.

Q: How did this project start? Was it a conversation between you and Brad?
A: I was the last one in. I knew Mariane a bit because we tried out play-dates, just as women and nothing to do with anything else. Then separately Brad had bought the rights to the book after they had met a few times and she trusted him and then I believe they got together and started to talk, it was like ‘OK, we’re going to make the movie, what do you think?’ and when it came to casting she mentioned me which was fantastic.

Q: What were your thoughts at that time? Were you worried about doing Mariane justice?
A: I was very worried. I’ve never been so nervous about anything. I work very hard but I’m very casual about it, it doesn’t keep me up at night but this one did. The night before shooting I was tossing and turning and imagining everything that could possibly go wrong. I felt bad that I was even assuming that I could play this woman that I respected so much and I felt humbled to a point of being unable to move. But her faith in me to do it really helped me so much and I do believe that even if you don’t think you are the best person for it, but if you know your heart is in the right place and you know you really care I do think there is a lot to that, so I tried to remember that.

Q: You had obviously established that friendship and trust with Mariane. How long did that take?
A: Well, like I said we met with this idea of having a play-date. When we first got in touch years ago we were both single Moms so the idea is ‘let’s get together for the kids.’ So our relationship started that way and it will continue to grow that way. It is a very strange thing to do a movie and do a movie that is important to you and very early on in it realise that you are doing a movie about one of your great friends. And you are actually having to show the world and interpret for the world the worst time in her life and something that this little boy, who I’ve come to really care about, is going to grow up and see. So it was all of that. But in the end we have a film that I’m really proud of and most importantly I feel very fortunate to have this friend in my life.

Q: How crucial was it that you had experienced pregnancy so that you could put yourself in Mariane’s shoes at that particular time?
A: I think it was very useful. On a practical level, I think if you’ve never been pregnant, you can over play pregnant and you can do a lot of different things with pregnant. It was almost unfathomable to me how she could get through it all as a pregnant woman. I mean, she is pregnant and that’s a huge deal and in the last few months you need less stress, more sleep, all of that. But Mariane has no self pity and I’m sure that if you ask her, she would say that she could never allow herself to think that he wasn’t coming home and she knew she was pregnant, she is a responsible woman, and she had to remind herself to eat, to take care of herself and her baby and get through it and focus on trying to find Daniel. And really, as much as anything, it was so emotional for me because in preparing to do it, it was right after I had given birth to Shi and that was such a special time and such a special time with Brad. And to have your baby born and look at your baby and look across the room at the other parent and to know that somebody took that away from her, infuriates me.

Q: What was it like filming it in Pakistan and India?
A: I love those parts of the world and I love to travel. I much prefer that to a big fancy trailer and a Hollywood studio lot. So I was so grateful to be there and that’s what we all loved about Michael as a director and knew he would bring authenticity. And that was so important. And it was wonderful. We all lived in the house, we had no separate trailers and we never left to go to lunch or anything, in a separate builiding, we were in that house the whole time and that helped us to bond and to create the atmosphere that you see in the film. We had one room in the house that kind of had some make up in it and some clothes changes. But if you walked out of that door you might be on film! (laughs). So it was great.

Q: What do you think the film is saying to the world?
A: I think it says a few things. One of the things that drew me to it, separately from her, was this idea of this mix of faiths and backgrounds. At a time in our lives when we are so quick to judge each others and be so full of fear, because of the circumstances there you ended up with a house full of people who were Hindi Christian, Jewish, Buddhist, Muslim, and all from different backgrounds, together to then try and help try this other person from another faith and another background. And the friendships that formed were incredibly strong. To this day Mariane and Captain, who is a Pakistani Muslim man, are very close. And he’s very close to Adam and this is the person from the same background and same religion of the man who interpreted that religion in another way and took this baby’s father and this man is making it part of his life to protect and ensure that he does everything right by this family.

Q: So a broader message would be?
A: We need to be open minded to understand that there are lots of different levels of things going on and we shouldn’t be so quick to judge – and certainly not to judge a whole race, a whole religion or a whole people - and a lot of that is going on. And the way Mariane handled this thing that happened to her was incredible and she did not go inside herself which she could so easily have done. Just a few days after she heard that Daniel had been murdered she came forward to say ‘I love Pakistan, there are ten other people that died and they are all from Pakistan, so they are suffering as much as we are.’ I mean, who comes to that? Who comes to that that quickly? It’s amazing. But then, she’s an amazing woman.

Q: There’s a remarkable scene when you find out the dreadful news that he’s died. What were you thinking about doing that?
A: There was something about that night. It was like we woke up that morning and it was the same as it was years before, when we heard the news about Danny. Even the actors I was looking at off camera had tears in their eyes. It had nothing to do with acting, it was the thought that somebody would do that to another human being and what that must have been like for Mariane and what that moment will be like for Adam, that broke us, and it was just a really emotional night.

Q: How is life in general for you?
A: Great! You know I haven’t worked since A Mighty Heart and it’s great to be home. And it’s great for Brad to be home now and me to be working a little. But he’s a really great father and a real hands on father and we are really enjoying the children together.

Q You’re still doing the work with the UN…
A Yes, I always work with refugees and I think they are the most amazing people and it’s a privilege to spend time with them so I will always. But I have gotten more involved…I’m focusing more on justice and I’ve become a real student of the international criminal court.

Q: Are you more hopeful now or has doing this work for the UN made you a less optimistic person?
A: I think since I started this work the world has become increasingly out of control and certainly my own country being involved in war. And I’ve seen a lot of things not heal properly. And I see a lot of things. Even in Cambodia, I still do a lot of work in Cambodia, where we started a millennium village and we’re doing work to protect the environment and we’ve got people from many different – one person from one country comes in and tries to build a damn and tries to sell it to some guy or some corrupt government official and somebody else comes in and wants to do some gem de-mining and somebody else makes a deal with somebody else. It’s trying to keep the balance because you realise there is so much corruption, so yeah, I’m not disheartened but I am definitely getting much harder to feel like, yeah a well is nice but if there is a Janjaweed member who is going to go in and take the pipe to make it a flagpole the well means nothing. Something else has to be done.

Q: How do you balance all of these things in your life? You mentioned you’re working again..
A: Well I haven’t worked for nine months, so I’ve been balancing kids and doing everything and then I work. I’ve signed up for two films this year and they are both two months each. The one in Prague is called Wanted and it’s with James McAvoy who is very good. I like the story and it’s kind of one of those wilder, darker ones. And really it’s great a great excuse for me to get strong and healthy and run around forget heavy things for a while.