Catherine counts Jenny as one of her favourite designers and is often spotted in her beautiful pieces.
While Jenny has a policy not to discuss any celebrity clients, she admitted that she works directly with Kate on her outfits. "It's always quite a collaboration," she told WWD.
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She also admitted that she was fast asleep when the royal wore what quickly became known as The Fern dress to a state dinner in New Zealand last week.
The designer was in New York showing her new bridal collection and realised when she woke up.
"Sometimes when we dress celebrities, there are always loads of Twitters and things like that when I wake up, I think, 'Oh right, she wore it,'" she explained.
Jenny's classic, feminine aesthetic perfectly embodies Kate's sense of style.
Their partnership started three years ago, when Kate stepped out in a stunning floor length blush pink sequinned gown for the ARK gala dinner.
She has since worn Jenny Packham both daywear and red carpet gowns on several occasions. Most notably, she worn her cornflower blue polka dot dress for that famous appearance on the steps of the Lindo Wing holding baby Prince George last summer.