"It really shows you just how many people take notice of what Prince George is wearing," Katie Rose of Olivier Baby tells PEOPLE

Credit: Max Mumby/Indigo/Getty; Courtesy: Olivier, Mayoral

From the palace to the polo field, Princess Kate and son Prince George are breaking tradition and changing the Royal rules. Subscribe now for an inside look at their adorable adventures only in PEOPLE!

There’s posh George, and there’s polo George. And in either adorable look, the nearly 2-year-old prince – this week’s PEOPLE cover star, alongside his mum, Princess Kate – is bound to make a serious splash.

A day after wearing his historic Trooping the Colour outfit of a multi-generational blue onesie steeped in royal heritage, George tumbled around a polo field – and unwittingly showed yet again how he s become the prince of promotion.

“We completely sold out overnight,” says Katie Rose from Olivier Baby, the British children’s wear designers behind George’s $100 blue cardigan. “It’s incredible. It really shows you just how many people take notice of what Prince George is wearing.”

“It’s been amazing. Completely amazing,” Rose tells PEOPLE. The knit sweater, which features a white star on the back, is only available to pre-order now.

RELATED VIDEO: Prince George’s $100 Cardigan Sells out ‘Overnight’

But the prince’s outfit was not strictly British-made. Like his sister Princess Charlotte, who has worn several pieces with a Spanish flavor, George was also decked out in a Spanish brand.

His $40 belted cotton Bermuda shorts were by Mayoral, a 74-year-old family firm from Malaga, Spain. We were thrilled to see Prince George wearing the shorts,” a Mayoral spokesperson tells PEOPLE. “It was a surprise, but a lot of children all over the world wear our clothes.”

They include the son of Real Madrid star soccer star Cristiano Ronaldo, Miranda adds.

And there’s no doubt that ubiquitous shoe of summer, Crocs, is also about to get a sales boost, after the future king was seen running around in a $30 pair of navy Crocband Clogs.

“Being a royal baby is a tough job, with a lot of pressure, so we’re thrilled to see Prince George finding his fun in our Crocband clogs,” cracks Andrew Rees, President of Crocs, Inc.

“They ve become a best-seller, thanks in part to the ‘Prince George effect,’ ” he adds.

For much more on Princess Kate’s sweet bond with Prince George – and how they’re both changing the royal family – pick up this week’s issue of PEOPLE, on newsstands Friday

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