London: Actress Katherine Heigl's mother kept the star in line when she was growing up by threatening to send her off to a convent if she missed her curfew.

The 33-year-old's mother Nancy insisted her daughter was always home by 1am in a bid to keep the blonde beauty out of trouble. And Heigl always adhered to the rule - because she feared she'd be enrolled in a Swiss nunnery if she didn't make it home on time, she reported.

"Katie believed it for a very, very long time, and that's the most important thing. I believed I would do it, and she believed I would do it... We go to Switzerland. We go to the bottom of the mountain.

"We take away all her clothes, we put her in a cloth sack, we put her on a donkey and send her up to the top of the mountain, where she doesn't get to talk to anybody on a regular basis but will occasionally get a letter from me saying, 'How you doing?," Nancy said.

But Heigl said she finally got fed up with her mother's rules and moved out at 22 after realising all her friends weren't tied down by the same restraints.

"I had this boyfriend, and we were really serious. I'd be over at this house and it would come around one, and I'd be like, 'I gotta go. I got this curfew.' One night, he just looked at me and was like, 'What the hell is wrong with you?'," said Heigl.