The case of Kate's mystery dress designer!

With the Royal Tour of Australia and New Zealand coming to an end, not much has been more talked about during their time here than The Duchess of Cambridge's fashion choices.

Said to be worth $2 billion to the British fashion industry alone, Duchess Kate's wardrobe is obsessed over from the designer, to the colour, to the length - every detail reported to within an inch of it's life.

No designer has come forth to claim Kate's yellow sundress that she wore at Taronga Zoo in Sydney. Source: Getty

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So it comes as a surprise then to find one designer choosing to remain silent on the issue, and choosing not to ride the wave of publicity that comes with The Duchess wearing your goods.

The item in question is the pale yellow dress that Kate wore on Easter Sunday when she visited Sydney's Taronga Zoo with Prince William and son, George.

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It's not the first time she has worn the dress either, first seen in 2012 during the Jubilee Tour when she wore it to the Solomon Islands.

But no-one knows who made it, only that it’s from an “independent British dressmaker”.

Kate wearing the mystery dress with Prince George during their visit to Taronga Zoo. Source: Getty

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Kensington Palace is yet to reveal the designer, but industry insiders suspect the designer is Angela Kelly, The Queen’s personal assistant and senior dresser, who also handpicked Kate's jewellery for her trip Down Under.

“(Kelly) knows most of the pieces in the Queen’s private collection,” said a Palace source.

“Her understanding is crucial because this trip will be about Kate appearing more Royal than ever – you can expect to see a lot more tiaras and the Queen will be watching closely.”

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Kelly has designed many of the Queen’s outfits since 2002 and reports in February suggested the Queen had offered Kelly’s services to the Duchess in order to employ a couture wardrobe with lower hemlines during the tour.

A source told Grazia UK in 2012 that the piece was "commissioned" by The Duchess.

“This dress was a piece commissioned by Kate. She likes to have a few pieces that are one-offs and that she has had some input in, so she asked the Queen’s tailors for some help … They worked on it together after she went to them with ideas of colour, fabric and style.”