The duke is believed to have told his wife the yellow wool-crepe dress by Roksanda Ilincic she wore as they embarked on their first official Australian visit made her ''look like a banana''. This follows his sledge on her sartorial choices in New Zealand when he said her emerald green Erdem coat was ''a bit bright''.

For their visit to the Blue Mountains, she chose a white and navy Diane von Furstenberg silk jersey wrap dress complete with her hardy Stuart Weitzman cork wedges.

After the first photos emerged, the Balinese-inspired day dress sold out on Diane von Furstenberg's official website in eight minutes. There are only sizes 12 and 14 left on the virtual racks of other high-end fashion e-tailors.

Her heels, which she first debuted at the London Olympics, continue to be one of the American designer's best-selling styles to date, and on Thursday, Sydney shoe lovers flocked to the recently opened boutique to snap up a pair.

Celebrity stylist Johnny Wujek, who arrived in Australia at the same time as the royal couple, said Catherine shouldn't listen to her husband when it comes to wardrobe choices.

''She's fearless but also always looks so effortlessly stylish, and that is something every woman should be encouraged to aim for when it comes to what she wears,'' the man who dresses Katy Perry, the Kardashian sisters and House of Cards star Kate Mara said.

Wujek added that her smile was the best accessory the duchess owned. ''Her mega-watt smile is infectious, and unlike her jewels, it's not on loan from the Queen.''