The 74-year-old talked about her first bra fitting in an episode of Sky 1's Little Crackers.
She said: 'People will be shocked to learn that I wasn't always the confident, feisty blonde that I am today - and how two of my greatest assets were the bane of my life.'
The show will look at key moments in the lives of some of the UK's best-loved celebrities.
She added: 'After more than 74 years on this planet, how do you choose one moment that changed your life? There have been so many.'
The episode will air later this year.