Steve Pratt discovers more about the role which had Angelina Jolie's nerves jangling as she prepared to play the real life role of Mariane Pearl, wife of the journalist Daniel Pearl who kidnapped and murderd.

ANGELINA Jolie has never been so worried about anything as her latest role. Portraying a woman she considers both a close friend and a remarkable human being weighed heavily on her. She plays Mariane Pearl, the wife of murdered journalist Daniel Pearl, in A Mighty Heart. The role was, says the actress, both an honour and a huge challenge. "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," she says.

"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 the woman that I respected so much. I felt humbled to a point of being unable to move. But her faith in me really helped me so much.

"I do believe that even if you don't think you are the best person for it, 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."

Imagine how anxious she must have felt when the finished film was screened for Mariane. Again, Jolie describes her state as "incredibly nevous".

Then she was "hugely relieved" when Mariane told her privately that she was thrilled with director Michael Winterbottom's film and indeed her performance. She said so publicly after A Mighty Heart received its world premiere at this year's Cannes Film Festival.

"As soon as Mariane was fine, then I was fine," says Jolie.

The film is based on Mariane's book, telling how she met and fell in love with Daniel Pearl and of the dark days of the kidnap while 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. 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 Pearl was abducted, Mariane was six months pregnant and now has a five-year-old son Adam. Jolie and Pitt have four children, Maddox, six, Zahara, two, one-year-old Shiloh, and Pax, three.

"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 they got together and started to talk," recalls Jolie. "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 met his contacts in the run-up to his kidnap, and also in India, where the Pearls' house in Karachi was recreated.

"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. "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. "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. So it was great."

Jolie says that life in general is "great" now. "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're really enjoying the children together," she says.

The star of Tomb Raider, Alexander and an Oscar-winner for Girl, Interrupted is a goodwill ambassador for the United Nations High Commission for Refugees. She's travelled the world highlighting the plight of refugees.

"I always work with refugees and 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.

"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."

* A Mighty Heart (15) opens in cinemas on Friday.