Diana, Princess of Wales’s black sheep jumper has sold for 1.14 million US dollars (£920,000) at auction.

The red jumper which a newly-engaged Diana wore to a polo match in June 1981, was sold for 1,143,000 dollars by Sotheby’s in New York, easily outstripping its 50,000 – 80,000 dollars estimate.

The jumper, which shows a black sheep among a row of white ones, was discovered in an attic in March by designer Joanna Osborne.

The auctioneers did not disclose the identity of the winning bidder.

Sotheby’s described the jumper as having “whimsical black and white sheep motif” and  was one of the first designs by Sally Muir and Joanna Osborne of Warm and Wonderful knitwear established in 1979.

The Sotheby’s catalogue note states: “Worn by Diana Spencer in 1981 to a polo match of Prince Charles.

“This lot includes two official letters, written in 1981, from Buckingham Palace to Warm and Wonderful politely explaining the jumper had been damaged and requested either a repair or replacement.

“Warm and Wonderful sent her a replacement sweater that she wore in 1983 to another polo match.”

Sotheby’s added: “Further investigation convinced the team: the damaged cuff, the shape, the single sheep at the shoulders, tiny variations in the sheep’s eyes which were individually sewn on…

“In conjunction with a photo matched authentication by Sotheby’s, this lost sheep jumper found in an attic is confirmed to be the original sheep jumper worn by Princess Diana over 40 years ago.”

Online bidding opened on August 31, the 26th anniversary of Diana’s death in a Paris car crash.