keira knightley elle uk photo march 2011.jpg

It seems no matter how many millions she may have in the bank, splurging on designer duds is still a big decision for Keira Knightley. According to the actress, she only spends big on high-end clothing if her mum says it's okay. In a new interview with British Elle, she reveals how she only bought the most expensive piece in her wardrobe - a £2,795 sheepskin coat from Burberry - after her mum gave her the nod.

"My mum was like, 'You cannot spend that amount of money on a coat', and I was like 'No, you're right I can't, I can't'. And then literally it was months, months of thinking about it and thinking 'I'm not going to do it, I'm not going to do it.' But then she said 'Right, if you're going to buy it, you have to wear it all the time'," she said. "I wore it everyday last year and I'm going to wear it every day this year".

You can read the full interview with Knightley in the March issue of British Elle when it goes on sale Wednesday.