Crowning moment for Aussie fashion as royals touch down

Last time Meghan, Duchess of Sussex wore Karen Gee in 2018, the label's website crashed within moments.

That didn't stop the designer totting up a more than 300 per cent surge in sales for the royal-worn dress in the months that followed.

"Demand was immediate and global," Ms Gee said on Tuesday.

When the duchess landed in Melbourne on Tuesday, the Sydney designer was delighted to glimpse another one of her dresses getting a royal run.

"It is not something I ever set out to achieve ... for me it always comes back to the same thing - creating pieces that women can return to."

A picture of the royal now fills the front page of the label's website, captioned "as worn by Meghan, Duchess of Sussex" along with a "SHOP NOW" button.

The dress costs $1250, with a skirt and bomber jacket ensemble from Melbourne brand St Agni, also worn by Meghan on Tuesday, costing $1888.

Seven Australian brands worked their way into the Sussexes' wardrobe on the couple's last visit Down Under, for the 2018 Invictus Games.

Back then, the duke and duchess were newlyweds and full-time working royals, yet to step back from blue-blooded life, move to California and drop bombshells on Oprah.

But the adoring crowds gathering at the couple's engagements on Tuesday suggest the intervening scandals have not sapped much power from "the Meghan effect".

She totalled the website of a brand she wore to her engagement in 2017 and sold out coats, scarves and bags within hours; one Welsh denim designer had to find a bigger factory in January 2018 to meet the demand Meghan had generated.

Outland Denim, an Aussie brand employing women at risk of being trafficked into slavery, hired 46 new seamstresses after Meghan pulled on their jeans five times during her 2018 visit and boosted their sales by 640 per cent.

"It brings a level of attention that is quite unique ... in the way it connects with women around the world," Ms Gee told AAP.

Melbourne-based label Saba tried to cash in without the duchess even wearing them, advertising a dress similar in style, but cheaper and more available than the Dion Lee number she actually donned.

The couple's four-day tour will next take them to Canberra and Sydney, where eagle-eyed fashionistas will look out for local labels on an Aboriginal walking tour, speaking engagements, an exclusive retreat, a harbour cruise and a rugby match.