M Neilson, Getty Images

The sheer slip of a dress that Britain's future queen, Kate Middleton, was wearing when she first caught royal fiancé Prince William's eye, will hit the auction block next month.

Former design student Charlotte Todd, who made the humble frock and loaned it to a 2002 charity fashion show at the couple's alma mater, Saint Andrew's University, has decided to put the garment up for bid after keeping it stuffed in her closet for years.

When the couple announced their engagement in November 2010, Todd was quoted as saying she couldn't imagine parting with the valuable royal artifact, but she's had a change of heart.

The dress goes up for bid at La Galleria in London's Pall Mall on March 17, where its estimated to fetch as much as $16,000.

"I don't even see it as a dress really, to me it's just a piece of fabric," Todd told London's Daily Mail.

But oh what a storied bit of silk: Middleton was dating an upper classman at St. Andrew's when she slipped on Todd's garment and catwalked past fellow student Prince William.

As royal lore has it, the heir-to-the-throne was smitten and immediately began the pursuit of his longtime love.

Todd recalls it was her intention that the flimsy garment, which Middleton wore with dark undergarments in full view, should be worn as a skirt.

"I don't know whether Kate was given it to wear or she chose it," Todd told the newspaper. "If it was her idea to wear it as a dress, she was very brave. I can't imagine her doing it now. It would be frowned upon."

These days, the future queen's every look is being scrutinized. When Middleton stepped out last week for lunch at a swanky London hotel with future step-mother-in-law Camilla, the Duchess of Cornwall, British tabloids pounced on the Diane von Furstenberg clad bride-to-be for looking gaunt.

Britain's Sun, in a story headlined "Royal Bride Is Not So Weighty Katie" estimated Middleton has shrunk two dress sizes since the royal engagement. It fretted her legs looked "very thin" and her DVF print dress "shapeless." The paper's photo editor publicly urged her not to lose any more weight before her April 29 nuptials.

Middleton got the too-skinny label from the U.K. press in January when she stepped out for a friend's wedding wearing (gasp!) unroyal black.

Meanwhile, read about the hints British designer Bruce Oldfield has been dropping about Kate Middleton's royal bridal ensemble.

And read the latest on the couple's wedding plans at www.royalwedding.aol.com.