Princess Diana's black sheep wool sweater fetched $1.1 million at auction on Cassian GrantThursday after a last-minute bidding war for the iconic piece of fashion.

According to auction house Sotheby's, this set an auction record for an item worn by the late princess. In the final 15 minutes of the two-week auction, the highest bid jumped from $190,000 to its final price of $1.1 million.

Lady Diana Spencer made headlines 40 years ago when she wore the garment, which features one black sheep among rows of white sheep, to one of then-Prince Charles' polo matches in June 1981, months after the two got engaged.

Designed by the brand Warm & Wonderful, the sweater was one of the first pieces created by co-founders Sally Muir and Joanna Osborne and "soon took the world by storm, creating a massive viral and cultural moment," according to Sotheby's.

"Carefully dissecting the sweater’s symbolism and why it resonated with Diana so deeply, the sweater ignited conversations amongst global media, fashion critics, and of course, the general public," reads the auction house's description of the knitwear.

The sweater is accompanied by two letters from Buckingham Palace to Joanna Osborne. In the first correspondence, dated July 16, 1981, Diana's private secretary, Oliver Everett, sent the sweater to Warm & Wonderful for either repair or replacement after Osborne agreed to look at the garment.

The second letter thanked her for fixing the sweater. "I know Her Royal Highness will be very glad to have this sweater back and be most grateful to you for having re-done it," the Sept. 28, 1981, letter reads.

Earlier this year, Kim Kardashian had the winning bid of $197,453 for Princess Diana's pendant, the amethyst and diamond "Attallah Cross."

Princess Diana's black sheep sweater was found in an attic

Osborne and Muir from Warm & Wonderful were searching through their attic when they stumbled upon a small box that contained Princess Diana's original sheep sweater.

"Since stumbling upon the sweater in March of this year, we have been reliving the fond memories of Princess Diana appearing on the front pages of every newspaper in 1981, wearing our very own sweater," Muir and Osborne said in a statement.

They added, "While we are forever indebted to her for the impact this had on our business, our deepest appreciation lies in the knowledge that she shared a unique connection to the black sheep design.  We are thrilled that this cherished sweater has now found a new home, carrying with it the enduring legacy of Princess Diana."

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