Princess Diana wore when she danced with John Travolta at the White House in 1985
John Travolta and Princess Diana
| Credit: In this Nov. 9, 1985 file photo released by the Ronald Reagan Library, actor John Travolta (L) dances with England's Princess Diana (R) at a White House dinner in Washington D.C. Ö(CREDIT: RONALD REAGAN LIBRARY/AP)

Queen Elizabeth and her sister Princess Margaret's childhood dresses and one of Princess Diana’s most iconic gowns will be discussed during a special online chat this week.

Royal curator Eleri Lynn would typically showcase the treasures of the unrivaled collection to fashion designers, students, historians and the general public in person, but with the palaces closed due to coronavirus, she has teamed up broadcaster and historian Lucy Worsley to open a virtual window into the collection.

The one-hour intimate Crowdcast talk, which airs Thursday at 2 p.m. ET, is free to the public, but Historic Royal Palaces is asking for a donation if people feel they can contribute. (Register for the talk here.)

“It’s a way of opening up the collection,” adds Lynn. “One of the joys of my job is to share the collection with people."

Central to their presentation is a previously unseen pair of cute Liberty-print dresses, which Historical Royal Palaces, the charity which looks after ceremonial and other regal clothes, has acquired.

“The princesses wore matching floral dresses for much of their childhood," Lynn tells PEOPLE. "These are like any little girl might have worn in the 1930s."

The dresses are from 1936, the year of the abdication of Queen Elizabeth's uncle Edward VIII, which was a tumultuous moment that thrust Elizabeth's father, and therefore herself, directly into the line of succession.

“It was even more important to convey them as an ordinary family unit,” says Lynn, who is chief curator of the Royal Dress Collection. “There is something quite profound about a little girl who was suddenly heir to the throne."

Liberty Print Royals
Princess Elizabeth's Liberty-print dress
| Credit: Historic Royal Palaces

"The dress is faded, and altered, which shows she liked wearing the dress and was active in it. And, as she grew, they didn’t get a new one, they altered this one and let it down and let it out. It shows a certain thriftiness, which we know is still there today.”

Another recent new addition to the palace is the Victor Edelstein gown that Princess Diana wore when she danced with John Travolta at the White House in 1985. But it won't be held up to be shown during Thursday's online chat.

Travolta Dress
The Victor Edelstein 'Travolta' Dress
| Credit: Historic Royal Palaces

In fact, it has been in a quarantine of its own in the palace’s “isolation room” for several months. Items are placed there soon after they have been acquired.

“My worst nightmare would be a pest infestation from a clothes moth or a carpet beetle," Lynn explains. "So we put them in isolation, wrapped in conservation material and then place them in the freezer. That gets rid of any infestation and any eggs and then we leave it out to thaw before transferring it to its permanent home.”

John Travolta Dress
The dress in its box in the "isolation room"
| Credit: Eleri Lynn

The Travolta dress was “nearing the end of its isolation journey” when lockdown began. When the U.K. lockdown was imminent, Lynn dashed around Hampton Court Palace taking photos of some of her favorite objects.

"Anticipating that we might have to pivot our public engagement online, I was opening boxes and snapping away. This is that same tour I might do with students or designers, but takes place with Lucy on Thursday," she says.

Of the Diana dress coming "home" after the charity bought it last December, she says, “The collection stores are in Hampton Court Palace, but the space where we often display our fashion items are in Kensington Palace, which was Princess Diana’s former home.”

“Diana is still considered very relevant, particularly her influence on the younger generation of the royal family and their humanitarian activities," Lynn adds. "Clothing is not a trivial matter but tells us of the values of the times and the people. So much of the image-making is about what they wear and conveying their messages and their values through their clothes.”

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A woman who knew all about messaging and iconic clothes was the Queen's late sister Princess Margaret. Lynn will be talking about a luminous ready-to-wear dress from Horrockses that Margaret wore for a photocall in the Bahamas with husband Lord Snowdon.

"She was conscious of image-making and how her clothes would be reproduced in the media. The bright pattern came across very well in print," she says.

Liberty Print Royals
Princess Margaret and Lord Snowdon
| Credit: Historic Royal Palaces

“Princess Margaret helped popularize the ‘new look.’ In 1947, Christian Dior came out with this collection that included long floaty skirts with tiny cinched-in waists," Lynn says. "A lot of people were horrified by it, but Margaret loved it and personally made it fashionable in Britain. There was a quote around at the time that said, ‘What she wears is news.’ She had a massive influence on what people wore.”