An evening dress worn by Diana, Princess of Wales in 1985 has sold at a Hollywood auction for almost $1.15m – more than 11 times its estimate and a record price for one of her dresses, according to the Guardian.

The black and blue ballerina-length velvet evening dress by the Moroccan-British fashion designer Jacques Azagury was sold at Julien’s Auctions in Hollywood for a total of $1,148,080 (£907,000).

The garment, which Diana wore at a dinner at Palazzo Vecchio in Florence while on a royal tour with her then husband, Charles, had been expected to sell for $100,000.

The outfit, which came complete with shoulder pads, a blue organza skirt, a large bow and a sash, is now by far the most expensive dress worn by the late royal sold at auction. The previous record holder, a 1991 velvet gown by Victor Edelstein, fetched $604,800 in January.

The identity of the buyer of the Azagury dress, which came with a matching illustration, is unknown.

Diana wore the dress at a dinner hosted by the mayor of Florence in April 1985, and again to the Vancouver Symphony Orchestra in 1986. The ballerina skirt was considered, according to the auctioneer, as a “nod to Diana’s love of dance and her being a patron of the English National Ballet”.

It was sold at an event on Sunday night titled Julien’s Auctions and Turner Classic Movies Present: Hollywood Legends. The catalogue described it as a “beautiful, romantic ballerina-length evening dress”.

It said: “With padded shoulder pads features a black velvet bodice with embroidered stars in metallic thread made from Jakob Schlaepfer fabric with a two-tier royal blue organza skirt with a sash and bow. Diana would wear numerous dresses and gowns by Azagury, one of her favourites was an ice blue silk georgette minidress worn 3 June 1997 to Royal Albert Hall for a performance of Swan Lake.”

Azagury was introduced to Diana in the 80s by the then British Vogue editor, Anna Harvey. “She said, ‘Jacques I have someone I’d like you to meet’, and I looked and Princess Diana was standing there,” Azagury says on his website.

Describing Diana’s trips to his Knightsbridge atelier, Azagury said: “Her visits were very relaxed, she loved chatting to the girls here. She didn’t ask me to design specific dresses for her, she knew that she could come here and find something she’d love and that we could adapt it and create a unique dress for whatever occasion she needed.”