She once revealed that her best friend had 'boobs to die for' and bemoaned that she would have to wear a padded bra to achieve that kind of cleavage.
And yesterday, Fearne Cotton got her chance to see just how much of Holly Willoughby's bra she could fill.
She sent her friend into fits of giggles as she showed off a photo she had taken of herself in Holly's white maternity wear.
Boobalicious: Fearne Cotton shows off a photo she snapped on her phone of her wearing friend Holly Willoughby's maternity bra
Holly, 30, and Fearne, 29, shared the joke before filming an episode of Celebrity Juice, the showbiz panel show on which they captain the two teams.
Fearne got out her BlackBerry phone and showed her team members - comedian Rufus Hound and model Janice Dickinson - a photo of her wearing Holly's bra.
But then presenter Keith Lemon - aka comedian Leigh Francis - made sure the audience could see as the snap was posted on the big screen.
OMG! Holly looked a little mortified but couldn't help giggling as she saw the photo of her friend in her bra
A blushing Holly put her hand over her mouth to stifle her giggles as her father and son team mates - George and Larry Lamb - and everyone else laughed at the situation.
There also appeared to be fun and games behind the scenes as Fearne used her camera phone to take a picture of her and Dickinson, who appeared to be wearing a Princess Leia outfit.
Holly and Fearne have been good pals for many years and last December they gave an interview to Cosmopolitan magazine about their friendship.
Look at me: Fearne's team mates Janice Dickinson and Rufus Hound admire her photo...
... much to Holly's embarrassed amusement, as her team mates George and Larry Lamb also shared the joke
In it, Fearne said if she could swap any part of her body with Holly, it would be her breasts.
She said: 'She has boobs to die for. I have to stuff my bra or wear a big padded one.
'If I put on one of those dresses she wears on Dancing On Ice, I'd look like my brother in a frock.'
Ladies that lark about: Fearne and her team mate Janice - who was dressed as Princess Leia - posed for a picture backstage
