Anne Hathaway says it was a challenge to her "vanity" when she cut all her hair off.
The 30-year-old actress was forced to cut off her long brunette locks to take on the role of the tragic Fantine in new movie 'Les Miserables' and she admits it was a tough decision because she loved her hair.
Speaking at the world premiere of 'Les Miserables' at London's Odeon Leicester Square cinema, Hathaway said: "It was very difficult (to cut off all my hair). I found it very challenging to my vanity. But than as soon as it was done, I was fine with it. I had a good reason to do it. It was for my job, I didn't lose it to an illness. I didn't have to sell it for money."
In the movie, Fantine is forced to sell her hair so she can get some money for her young daughter Cosette.
Meanwhile, Anne's co-star Amanda Seyfried - who plays the grown-up Cosette - spoke of her nerves about seeing herself sing on the big screen because they had to do it live.
Amanda - who starred in 2008 musical 'Mamma Mia!' - said: "'Mamma Mia!' and 'Les Miserables' are so different, you can't compare. In 'Mamma Mia!' we got to record all of our vocals beforehand and then lip-sync and it was great and so much fun. But this was incredibly hard. I had a problem listening back to myself as I was singing so that was my biggest challenge."
Other stars to walk the red carpet at the premiere included Hugh Jackman, Russell Crowe, Eddie Redmayne, Helena Bonham Carter and Sacha Baron Cohen.
'Les Miserables' is released in the US on Christmas Day and around the world on January 11 2013.