Kate chose the Australian label’s cream lace Roamer Day Dress – which retails for $495 – from its upcoming Summer Swim 2014 collection.
The frock doesn’t hit stores until June but Naomi Watts wore it last month for a recent ad campaign.
Kate paired the dress with a pair of sky-high tan wedges, looking absolutely stunning as she toured the craft and sheep pavilions at the annual show.
It’s a big day for Zimmermann, which is likely to see an massive increase in sales thanks to the royal seal of approval – indeed, within seconds of the Duchess stepping out in the frock, the label’s website had crashed.
Kate has a proven ability to sell fashion – the Diane Von Furstenberg wrap dress she wore to the Blue Mountains yesterday sold out worldwide in just eight minutes.
