IN THE END, THE SURPRISE WAS THAT her move stayed a secret for so long. As it happened, Diana, Princess of Wales had been working with Christie's since last summer on a scheme to put her most sumptuous frocks into the hands of the highest bidders. Only last month, however, did Palace watchers discover that—determined to establish herself as a serious philanthropist—she had arranged for 80 formal dresses to be auctioned for charity. By Feb. 25, when Christie's unveiled part of the cache, the buzz was deafening. Insiders were predicting that proceeds from the June 25 sale in Manhattan would top $7 million, and a furious Di had lodged a libel suit against London's Express on Sunday, which claimed she meant to give only half the profits to pet causes—and line her hand-tailored pockets with the rest.

At its headquarters on Park Avenue, Christie's International chairman, Lord Hindlip, was adamant about Di's motives. Confirming that every cent—save what is needed to cover Christie's costs—will go to the London-based AIDS Crisis Trust (ACT) and Royal Marsden Hospital Cancer Fund and related U.S. charities, he said, "The sale reflects [Diana's] genuine concern for those who suffer from these maladies." Through Christie's, Di herself noted, "I am extremely happy to have this wonderful opportunity to raise money for charities...I am also delighted that these dresses which gave me so much pleasure may be enjoyed by others."

The bold gesture, it seems, was inspired by Prince William, 14. Before the Waleses' August divorce, he reportedly suggested that his mother sell her surplus finery. Diana, 35, dug deep into her closet—keeping just 10 of the ball dresses from her collection at Kensington Palace. "Involved every step of the way," according to Lord Hindlip, she plans to attend pre-auction fund-raisers in Manhattan and London, though she will skip the sale.

On the block will be frocks worn at official engagements from 1981 to 1994, as well as outfits seen only at private gatherings. Made for the 5'10" Di by designers including Victor Edelstein, Zandra Rhodes and Catherine Walker, the dresses are in sizes corresponding to a (lanky) U.S. 8 or 10.

Early in May, bidders can begin snapping up the 170 autographed catalogs ($2,000), the 5,250 hardcovers ($265) and an unlimited number of $60 paperbacks. Christie's will put the collection on exhibit in mid-June, and only those clutching catalogs will be allowed to see the dresses—or to bid.

As to how much the frocks might fetch, that is anyone's guess (catalogs will cite no estimates). "The staff is having a sweepstakes on it," laughs Lord Hindlip, adding that bidding could start at $5,000. But while her favorite charities will get the profits, it is Diana herself who may reap the biggest reward—shedding part of her rudderless past and putting a spin on the future.

LYDIA DENWORTH and SIMON PERRY in London and MARIA SPEIDEL in New York City

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