The Devil Wears Prada star admits she feared she was taking on too much when she signed on to portray Fantine in the blockbuster - because she had so little in common with the character, but she quickly found research material in tragic stories online.
The actress says, ""There's no way I can relate to what my character is going through. I've had a very happy and successful life. There's no children that I've had to give up, or keep!
""I tried to get inside her world and to do that I read a lot of articles and watched news clips of sexual slavery.
""I remember there was a police raid to one of the brothels and a camera crew came along and there was a crawlspace up in the ceiling that was so tiny; and 14 girls came out of it. They were all so tiny and scrunched up there together and when they came out they weren't shocked there was a camera there or worried about getting arrested. They were numb and unrecognisable as human beings. My heart went out to them.
""I came to the realisation that this injustice exists in our world and Fantine is probably just a block away. This is me honouring that this pain lives in this world and I hope that me honouring all of our lifetimes, like today, we see it end.""