There are a few things the British royals can’t travel without — like extra bags of blood.

The claim was made by Dickie Arbiter, former press secretary to Queen Elizabeth II and media manager for King Charles III and Princess Diana. Arbiter, who worked for the royal family between 1988 and 2000, appeared on Wednesday's episode of Hello! magazine’s "A Right Royal" podcast

"You’ve got to make sure that you’re covered in every eventuality," Arbiter said, "and the aircraft-carried blood as well. Blood, yes, for in the case there was a blood transfusion."

According to Arbiter, the late queen and her husband, Prince Philip, as well as Charles and Diana, traveled with packs of extra blood out of precaution. And it is believed the practice still applies today.

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Prince Charles with his press secretary, Dickie Arbiter, boarding a boat during a tour in Canada.

Dickie Arbiter, who worked for the British royal family, appeared on the Wednesday episode of Hello! magazine’s "A Right Royal" podcast. (Tim Graham Photo Library via Getty Images)

"There’s never really a guarantee that you’re going to get the right type of blood at your destination," Arbiter said. "So you carry it."

In addition, it was "standard practice" to carry "a black outfit."

"When I packed my own suitcase, there would be a black tie in there," Arbiter said. "You always think of the worst."

Looking back, Arbiter also told the outlet that it wasn’t unusual if Charles flew his own commercial plane.

Princess Diana laughing with Dickie Arbiter

Dickie Arbiter, center, with Princess Diana, worked for the royal family between 1988 and 2000. (Tim Graham Photo Library via Getty Images)

"If we were using the queen’s flight, invariably the Prince of Wales would pilot the aircraft," Arbiter said. "He was a qualified pilot, commercial. He doesn’t anymore, but he used to. The late Prince Philip used to, as well. Prince Charles would fly the whirlwind helicopters of the queen’s flight. [On] occasions, I’ve been on a flight and the prince would be upfront. The RAF [Royal Air Force] crew would take off and then he would go up front."

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"Younger royals tend to take private jets, senior royals don’t," he said. "If the late queen went to Australia with the late Prince Philip… if a plane wasn’t available, they would go British Airways, paying for it. It wouldn’t be given free. The first-class section might be turned into bedroom quarters."

Royal expert Shannon Felton Spence, who traveled with Charles and Camilla, the Queen Consort, in 2015, told Fox News Digital that traveling with vials of blood "makes sense." And the black outfit rule is standard practice.

King Charles and Queen Consort Camilla traveling by plane

Several experts said that it's standard practice for royals to travel with a black outfit, no matter the destination. (Yuri Cortez / AFP via Getty Images / File)

"The late Queen Elizabeth II was caught totally off-guard when her father passed away while she was in Kenya," Felton Spence said. "She didn’t have a black outfit to exit the plane in the U.K. Knowing that the world's photographers would be on her, a lady’s maid had to run a black dress up the tarmac to her so she could change before she stepped out. But it’s not just if a member of the family were to pass away. It’s any major dignitary throughout the world. Given how unpredictable that can be and the lessons learned from 1952 with the queen, they always travel with one appropriate all-black outfit."

There are other travel rules the royals allegedly live by. According to Felton Spence, when picking an airline or hotel, they always favor a British brand. In terms of hotels, Princes William and Harry prefer The Carlyle in New York City because their mother "loved it there" and "they love to feel that connection with her." And when it comes to flying, commercial is the way to go.

"They don’t want to appear to be traveling in luxury on the public’s dime," she said. "So, they do fly commercial whenever possible. Usually British Airways first class. If commercial isn’t possible, sometimes they are on a government plane."

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Prince William arriving at Princess Diana's favorite hotel in New York City

Prince William arrives at The Carlyle on Dec. 7, 2014, in New York City. The hotel was a go-to haven for his late mother, Princess Diana. (James Devaney / GC Images)

"I will say the one thing that is a little bit different," she said. "Harry especially likes to [use a] helicopter from one location to the other. I remember this being a big consideration when Harry visited New York in 2013. At Kensington Palace, there’s a big grassy field behind the palace that is used for helicopter access. So, the neighbors often know when they’re coming or going."

On the podcast, Arbiter said that the queen made a rule that Charles and his heir, William, couldn’t fly together. And it’s a rule that he said is still in place, but "based on judgment."

And they must always look their best.

Kate Middleton arriving in style wearing a creame suit

Kate Middleton, who is famous for recycling her wardrobe, always travels in style, royal experts say. (Chris Jackson / Getty Images)

"Sleep masks and eye treatments are a necessity for that fresh-faced look upon landing," Kinsey Schofield, host of the "To Di For Daily" podcast, told Fox News Digital. "Kate Middleton brings an entire entourage of people to do her hair and makeup, as well as to dress her and get her where she needs to go."

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Before embarking on their journeys, Schofield noted that members of the royal family are expected to learn some of the destination’s native language. She described how a "sweet and nervous" Diana charmed the hearts of many in 1981 when she delivered an entire speech in Welsh.

Princess Diana wearing a bright blue dress

Princess Diana is shown in Cardiff, Wales, after delivering a speech in Welsh. (Tim Graham Photo Library via Getty Images / File)

And aside from blood or a black outfit, sometimes spirits make it on the packing list.

"King Charles and Queen Consort Camilla have developed a unique tradition of bringing their own booze on their travels," said Schofield. "Of course, their invite did not say BYOB. This method is to ensure that no one spikes their beverages. The senior royals sometimes carry a bag of gin and tonic for Charles and red wine for Camilla."

The queen, who famously wore bright colors, "was not known for traveling light," royal fashion expert Miranda Holder told Fox News Digital.

Queen Elizabeth II is seen in London in May 2022

Queen Elizabeth II marks the completion of London's Crossrail project at Paddington Station on May 17, 2022. (Andrew Matthews / WPA Pool / Getty Images)

"[It was rumored she took] all sorts of things with her, from her daily afternoon tea to toilet roll to her own physician complete with spare bags of her very own blood," said Holder. "In the same vein, her wardrobe was meticulously planned down to the very last detail, so I cannot imagine the late monarch looking anything other than absolutely immaculate."

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"King Charles is also known to be a more extravagant traveler, having commandeered an old Airbus for his private travels resplendent with double bed and shower facilities to keep comfortable," she continued. "The king is known for his penchant for quality and workmanship, boasting a fine collection of bespoke Savile Row suits in his collection."

Christopher Andersen, author of "The King," echoed Charles’ more lavish approach to traveling.

King Charles and Camilla Parker Bowles at Braemar Games in Scotland

It is said that King Charles III has a collection of Savile Row suits. (Samir Hussein / File)

"Charles did occasionally fly commercial but with great reluctance," Andersen told Fox News Digital. "It didn't always go well. When a chartered British Airways 747 took a party of dignitaries to China for the handover of Hong Kong to mainland control, Prince Charles was horrified to find himself relegated to business class while senior ministers of his government sat in first class. It was a humiliating experience for the heir to the throne — one he has never forgotten. Charles wrote in his diary at the time, 'Such is the end of the empire,' I sighed to myself.'"

"William and Kate have to be commended on the fact that, even when traveling in an official capacity, they insist on flying commercial," Andersen said. "Not only does this dramatically reduce their carbon footprint, but it sends the message that they wish to economize at a time when their country is going through a severe economic crisis."

For Charles, no trip was complete without his alleged go-tos.

King Charles smiling and holding a teddy bear

Christopher Andersen, author of "The King," has long alleged that King Charles III travels with his childhood teddy bear. (Chris Jackson / WPA Pool / Getty Images)

"Charles has always had quirky tastes and fully indulges them on the road," Andersen said. "Traveling with his childhood teddy bear, a valet who indulges his every whim, his own monogrammed eating utensils and, though he has formally denied it, his own upholstered toilet seat and brand of toilet paper."