One of Princess Diana's dresses sold for a record-breaking $1.1 million. Here's how items like it are cared for before and after an auction.

• One of Princess Diana's dresses sold for $1.1 million at an auction on December 17.
• Business Insider spoke to Martin Nolan at Julien's Auctions about how clothes like Diana's are cared for.
• Nolan said it's "a huge sigh of relief" when the item is safely delivered to its new owner.

Princess Diana solidified her icon status in several ways throughout her life, from her commitment to helping those in need to her willingness to speak out against members of the monarchy.

But she was also beloved for her fashion, and just a couple of weeks ago, a buyer spent a lot of money to own a piece of her wardrobe.

On December 17, one of Princess Diana's gowns sold for $1.1 million at a "Hollywood Legends" sale hosted by Julien's Auctions and Turner Classic Movies. The final sale price was 11 times more than its original estimate, making it the most expensive dress of Diana's sold at an auction to date, according to a press release from Julien's Auctions shared with Business Insider. The release said the previous record holder sold for $604,800.

Jacques Azagury designed Diana's dress, which had puffy sleeves, a tulle skirt, and blue, sparkly embellishments covering the bodice.

The late Princess of Wales wore it at royal engagements in Florence, Italy, in 1985 and Vancouver, Canada, in 1986.

The Jacques Azagury dress is part of a slew of clothing and personal effects Julien's Auctions has sold in recent years, from Steve Jobs' Birkenstocks to a pair of Kurt Cobain's jeans.

According to Martin Nolan, the executive director and cofounder of Julien's Auctions, people are buying these clothing items because they find them more relatable than high-priced pieces of art.

"Everyone can relate to a dress or a pair of jeans more easily than a Monet or a Picasso," he said, adding that he believes that was the case for Diana's dress.

Nolan said Diana's dress had previously been donated to the New York Historical Society, so the proceeds from the sale will go back to the organization, with Julien's receiving a cut of the money.

Though people buy the items through Julien's Auctions, the organization acts as the go-between for buyers and sellers, with Nolan telling Business Insider that Julien's staff members act as "custodians and guardians of the pieces" before they find a new home.

"We enter into a contract with the seller, and they pay us a commission, and then we work for the seller to find the buyers and to sell for as high as possible," Nolan said. "We are all vested in the results of the sale given that we're commission-compensated."

To ensure the items sell at a high price point, Julien's Auctions exhibits pieces worldwide to garner excitement for the auction — which can involve complicated travel.

It's not simple to move items around

Julien's Auctions doesn't ship its items for exhibitions. Instead, an employee will travel with the items by plane, physically staying with the pieces until they are sold.

And as Nolan told BI, an expensive auction piece like Diana's dress would never go into checked luggage.

"If I'm traveling with the dress for an exhibition pre-auction, it would hand-carry with me," he said.

The pieces also need paperwork to go in and out of the country, as Nolan told BI. These papers are called ATA Carnets, though they're often referred to as Merchandise Passports, according to the International Trade Administration.

"When I would take it out of America, I would have to have it stamped at customs, and then when I arrive in the UK or France or Ireland or South America or wherever I'm going, they'll stamp it to say it's received," Nolan said. "And then I have to have an export stamp when it leaves that country and then an import stamp when it comes back to the USA."

"There's an awful lot involved, but it's because these are high-value items that are crossing borders," Nolan added.

The auction items are also heavily protected when they're transported to new owners

Julien's Auctions' customers are worldwide, as they can bid for items online, so the company ships some of the items after they're bought. But anything shipped has to be packed carefully to ensure it isn't damaged in transit.

Nolan said clothing is first packed in acid-free tissue paper before being placed inside a linen garment bag. It's then packed inside an additional garment box, giving it multiple layers of protection.

And in case any of those protective layers fail, Julien's Auctions' commissions are insured at high prices "to ensure garments arrive safely and in pristine condition," Nolan told BI.

Nolan said it can be stressful to have an item worth so much money, even temporarily.

"I'm the caretaker, and honestly, it's a huge sigh of relief when something iconic is sold and it's delivered safely to the new owner," he said. "Yes, they're insured and the check can be written and people are made whole, but it doesn't replace what this item represents."

"I would be devastated if anything happened to anything under my watch because it's such a huge responsibility, and it's a huge honor," he added.

Julien's Auctions is selling another piece owned by Princess Diana — an off-the-shoulder Catherine Walker dress — on January 18. The auction house estimates it will sell for between $100,000 and $200,000, but it already has a $100,000 bid weeks before the sale date.