Angelina Jolie almost turned down her latest film role because the subject – the kidnapping of a child and a woman’s betrayal – was too painful for her as a mother. But, as she tells Steve Pratt, she became fascinated by the story.

BEING a mother, Angelina Jolie found her latest screen role – playing a woman whose nine-year-old son goes missing – one of the toughest of her career.

Shooting the scene when she reports the child’s absence was the most difficult in the movie. “It’s such a serious fear, especially for any parent, that you just don’t want to physically do it,” she explains. “You don’t want to go up to a phone, pick it up and report a missing child. It’s horrible. So that was hard to do.”

The latest addition to Jolie’s own ever-growing family, twins Knox and Vivienne, are upstairs – “hopefully asleep” – while their mother talks about the Clint Eastwood-directed movie, Changeling, downstairs at London’s Claridges hotel.

She doesn’t say if her other half, actor Brad Pitt, is babysitting but, unlike other Hollywood A-listers, hasn’t sent advance word that personal questions will not be tolerated. If she thinks someone is overstepping the mark, she’s quite capable of dealing with it. How’s your health, someone asks, mentioning comments about how thin she looks in the movie.

“I don’t think that’s a question,” she says calmly, putting the lid on further inquiries of that nature. But she’s happy to talk about the family that she and Pitt have. In addition to the twins, there are two-yearold Shiloh and three adoptive children, Maddox, Pax and Zahara.

That’s unlikely to be the end of it. Can we expect to see her family expanding further? “I’m sure you can,”

she smiles.

Jolie has never been one to hide behind a publicist, perhaps being too honest for her own good. Interviews don’t only mention her work as a UN ambassador, but dredge up old quotes about her sex, drugs and rock’n’roll past.

She’s dressed in grey top and trousers with black boots. Her make-up is restrained and subtle, as befits the serious film about which she’s talking. Changeling is based on the true story of Christine Collins whose son went missing in 1928. Five months later the police returned a boy to her – that she knew wasn’t her son. The corrupt police department was hoping for good publicity by reuniting mother and son.

When she protested they had her committed to a mental asylum, along with other women who’d dared to go against the police. A subsequent court case led to the exposure of police procedure and a change in the law about committing people in asylums.

“It was a very hard film for all of us to make, but at the same time, because it was a true story and because these women went through so much, it was also very inspiring,” says Jolie.

Reading the script, her first reaction was to turn down the part. “I didn’t want to go into this project because it was too upsetting,” she explains. “But then afterwards I couldn’t stop talking about her. I found myself sitting with people wanting them to know about this extraordinary woman. You wouldn’t believe what happened to her, and what these people did to her in this time in our history.

“In the end, it became a story about democracy in action, about justice... even suffering a great loss and fighting through it and making a change for the future for other people, and questioning the government and the police. I found it very inspiring and really wanted people to know about her and felt like it was an extra piece of justice for her.”

That didn’t make filming it any easier. “As a mum, it was horrible,” says Jolie. “I had my kids with me as much as possible at lunch and, after a day at work, I’d just run home. I just wanted to be silly. I was so emotional that I found myself being very, very goofy with them. I was so happy that I knew where my kids were and that they were okay.”

Jolie answers questions with intelligence and good humour. Only when she mentions her late mother does she show any emotion, coming close to tears. She’s talking about playing the role of Christine Collins who, because of the period, had to keep her place rather than shout from the rooftops about the injustice.

“She had to walk a very, very fine line. And when she did speak out was when they locked her in the institution.

“So she had this real struggle to try to behave with these very corrupt people. She was also a single mother in 1928 which was a very difficult place to come from and didn’t command any respect at that time.”

Jolie’s had a difficult relationship with her father, actor Jon Voight, but was closer to her mother, whom she had in mind when playing Collins. “Her name was Marcheline but we called her Marshmallow, as a joke, because she was the most gentle woman in the world,” she says, battling to hold back the tears.

“She was really, really sweet and she would never get angry. But when it came to her kids, she was really, really fierce and so this is very much her.”

Her mother was far too young when she died at 58, she continues, although she’s grateful she lived long enough to meet most of her children.

“You can only think of that and focus on just how grateful you are,” she says.

“I’ve been so blessed to have healthy children and a great partner. We’re having such a wonderful time raising our children together. So, I remind myself of that whenever I think of what I’ve lost.”

Jolie can’t name any specific thing for which she’s fought as hard and with the same passion as Collins did in her search for her missing child. “I think when you make a commitment to have a child, you’ll do anything for them and anything to protect them,” she says.

“You naturally have that commitment made and hopefully it’s not tested. I know when I first started travelling and met refugees in Sierra Leone on my first trip with the UN, I remember coming back and meeting my mum and saying ‘I really want this to be discussed more.

I really want these people to have a voice’.

Her growing family and work for the UN Refugee Agency mean we’ll be seeing less of her on screen. She confirms that she’s cutting back on acting. She hasn’t worked for a year, plans to work for a few months and then doesn’t know when she’ll work again.

“I’m not going to make a retiring announcement but I have a big family and a lot of responsibility at home, and am very fortunate financially not to have to work all the time.

“So maybe one film a year, or once every two years. And maybe eventually, I’ll stop.”

■ Changeling (15) opens in cinemas on Wednesday.