Princess Diana's Belville Sassoon Floral day dress was thought to be lost to time, but now it will have pride of place in the virtual Princess Diana Museum.

The item was lot four at Julien's Auction on Thursday June 26, and was purchased by Renae Plant, who founded the museum to honor Diana's "humanitarian legacy, fashion history and personal life journey".

The bidding started at $150,000 and rose in fifty thousand increments to $350,000 where it sat for almost a minute waiting for the hammer to drop, before Renae – who was in the room at – raised her paddle for $400,000 (£291,000).

Including the buyer's premium of 27%,

As the item sold, Renae jumped up in joy before collapsing to the floor as the auctioneer confirmed her paddle number.

She had previously shared that this lot was her most wanted, as it is the dress Diana was wearing when an 18-year-old Renae met the Princess in Australia.

"It signifies who she was and envelopes the kindness, the compassion, and the humanitarian that she was," Renae told "And being the curator of the Princess Diana Museum, I feel that would come full circle."

The dress became a famous Diana outfit as she wore it on several occasions, and in particular when she would visit hospitals and sit with patients, leading to it becoming known as the "Caring" dress.

It also became a talking point as it became hard for the press to determine if the pictures were new or old.

Martin Nolan, the Executive Director and Co-Founder of Julien's, told that the dress had been sitting in the closet of a close friend of Diana's for decades.

After a previous auction, the friend reached out to Julien's after realizing the importance and legacy of this dress.

"I thought this Caring dress was never going to be seen," said Renae. 

"I thought this dress was lost in time, to be honest. It signified such an important time in my life when I met her, and the impact she had over me as a teenager, and I never in a million years thought that this would be ever, ever, ever available to be acquired."

A silk floral printed day dress designed by Bellville Sassoon, she was photographed wearing the dress on at least seven occasions between 1988 and 1992.

It features a blue crepe-de-chine material with a pastel floral print, high crew neck, ruched bodice, and knee-length skirt, with a zip closure that extends from the bodice to the skirt.