Leading British designer Stella McCartney is a favorite to design the wedding gown for friend Meghan Markle, when she marries Prince Harry at the royal wedding of the century Saturday at St. George's Chapel in Windsor.

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British bridal designer Carolina Castigliano told Page Six that she believes  McCartney, best known for her use of organic materials, precise tailoring and modern feminine clothing, may well have designed Markle's wedding dress.

She’s a “perfect fit for Meghan,” Castigliano said.

"She uses organic fabrics and her ethos is the same as Meghan's. Her style is very underplayed, her dresses are very clean in style, very much Meghan – and they are friends," Castigliano said in an interview with Page Six.

Castigliano also told the celebrity magazine that Markle will pair the wedding gown with a tiara from the collection of Princess Diana, Prince Harry's mother.

Getting to Know Meghan Markle

"I believe it will be a very straight, fitted dress, with a big 9-foot train that comes off the dress from the side to create the drama, and lace trickling down the top of it," the bridal designer told Page Six.

Bowing to past traditions, Markle also most likely had her wedding gown approved by Queen Elizabeth.