Julie Walters at World Premiere of Mamma Mia! held at the Odeon Leicester Square - Arrivals. London, England - 30.06.08

The Mamma Mia! star details the abuse she suffered at the age of ten in her forthcoming autobiography - and admits she kept it a secret for 25 years.

The 58-year-old claims she was abducted along with three other young girls, and the group was subjected to a sexual assault from an unknown assailant.

She says, "He tried to get us into a derelict house. He touched me. It was nothing horrific, but it could have been. It was the start of a sexual assault. There were three of us, plus a little one, and you'd think there'd have been safety in numbers. But we were so frightened of him, we would have done anything."

And Walters admits that writing her life story has forced her to re-examine her traumatic past.

She adds, "I only told my mum about it when I was 35. Writing about the incident made me feel sick. As an adult you look back at all the details you didn't understand then. Now, I know what he wanted. It's frightening."

Source: WENN