The style of the late Diana, Princess of Wales, will forever be a source of inspiration to many. But now, someone will actually own one of Princess Diana's most famous pieces: the 'black sheep' jumper that was once part of her everyday wardrobe.

The special item from knitwear brand Warm & Wonderful sold for an impressive $1.14 million (approximately £916,700) at Sotheby's auction house in New York this week, far exceeding the original estimated value of £40,000 to £70,000.

Part of the inaugural Fashion Icons auction, Diana's iconic jumper was up for sale alongside two letters detailing her love for the clothing item. In one of the letters, the princess referred to the jumper as her "much-loved knit"; the second was a thank you letter for her favourite wardrobe piece.

"Much to our amazement, the first we knew of Lady Diana Spencer wearing the sweater was when we saw her on the front page of one of the Sunday newspapers," Warm & Wonderful founders Sally Muir and Joanna Osborne recall. "Her influence was impactful almost immediately thereafter, leading to a surge in sales and public awareness of our small label, for which we will be forever grateful."

Warm & Wonderful stopped producing the style in 1994, but bought it back in 2019 when Jack Carlson, creative director of the American clothing label Rowing Blazers, approached Muir and Osborne with a request to bring it back. Carlson's love for Diana's fashion started as a child, when his family were living in Hampstead in the early Nineties and his mother bought an original jumper from the Warm & Wonderful Covent Garden stall.

"Diana is a personal style icon of mine," Carlson told Bazaar. "After living in Hampstead, North London, during the early Nineties with my family, it might have been inevitable. She perfected the art of mixing high and low and blurred the lines between menswear and womenswear."

He continued: "It seems to me that she thought about the semiotics behind what she wore, as well as the aesthetics. In a weird way, she was doing streetwear before streetwear was a thing — but at the same time, she was the archetype of the Sloane Ranger. She was all of these contradictions and that’s what made her so iconic. I think out of everything she ever wore, the two most iconic pieces are the 'Revenge Dress' and the Warm & Wonderful jumper."

The reissued style sold out instantly and was worn by Emma Corrin in the popular Netflix series The Crown, in which she played a young Diana.

So why is the princess' style so iconic, all these years later? "From her early years as a shy and reserved royal to her later years as a confident and independent woman, Princess Diana’s fashion choices broke the mould by reflecting the changing social climate and embracing evolving perceptions of femininity," explains Cynthia Houlton, Sotheby's global head of fashion and accessories.

"By combining high-end designer pieces with more attainable everyday apparel, Diana’s style led to a wave of imitation and admiration – which remains steadfast to this day – leaving an indelible mark on the fashion world and solidifying the Princess as an icon in fashion history," Houlton continues. "This exceptional garment, meticulously preserved, carries the whispers of Princess Diana’s grace, charm, and her keen eye for fashion."

She adds: "It’s an honour to offer this historic sweater in our inaugural Fashion Icons auction, placing it in dialogue with other memorable and culturally important items of clothing.