Anything the Duchess of Cambridge wears will sell out quickly and the expert suggested she is aware of her influence.
The mother-of-three will often support British brands and sport affordable high street looks.
“Kate is fond of championing British brands and she chooses well,” Kate explained.
“The items she wears sell out within minutes – labelled the Kate-effect’. Last month she wore a Pure Collection roll-neck cashmere jumper on a trip to Northern Ireland.
“This jumper, and styles like it, are now out of stock in John Lewis and on the Pure Collection site.”