King Charles' rarely-pictured 'secret' feature inside 775-room London home

King Charles ' royal residences such as Sandringham and the Palace of Holyroodhouse may be open to the public for tours, but they remain shrouded in mystery when it comes to the royals' private quarters.

The Royal Collection Trust admitted that they are often asked to divulge some secrets, prompting them to show off a rarely-seen area of Buckingham Palace.

"One of the best-known secret passages at Buckingham Palace is one that connects the private apartments to the State Rooms, and it enables members of the royal family to arrive at events almost unseen," explained a curator in the Instagram video.

The caption added that the "secret" door is a popular detail among visitors, adding: "See (just) behind it with our curator, Sally!"

© PA Images / Alamy Stock Photo

The white walls covered with gold panelling were broken up by a large mirror and side table topped with the Sèvres vase, which concealed the door. When closed, guests would have little clue that it hid anything, but Sally revealed a mini waiting area behind the mirror with wooden floors and a golden door leading off it – the perfect spot for royals to make their surprise entrance.

When fans expressed their concerns that people entering and exiting the room via the door may damage the beautiful decor, the RCT replied: "Don't worry, all of the works of art on the cabinet surface are fixed so they can't fall off when the door is moved."

Buckingham Palace

The exterior of the royal residence is one of the most iconic landmarks in London but inside the 775-room property is even more impressive.

© WPA Pool

Features include a post office, the ballroom that plays host to grand banquets, the State Dining Room which was used during the Prince and Princess of Wales' wedding, and a royal conservatory which houses a swimming pool .

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The building has been undergoing major renovations including rewiring, removing asbestos and installing new boilers, costing over £300 million. See some of the changes in the video...

Charles has been keen to make royal residences more accessible to the public. Most recently, the East Wing opened up to guests, with 6,000 tickets going on sale for a tour through the Centre Room, Yellow Drawing Room and 240-foot-long Principal Corridor, as well as the 19 State Rooms.

One of the biggest attractions of the tour was the newly-restored Centre Room, which leads to the famous balcony with views down the Mall.

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The royals have celebrated coronations, weddings, and jubilees from the room and it is where the King chose to record his last Christmas Day message in December.

Explaining the history behind the room, Caroline de Guitaut, Surveyor of the King’s Works of Art at the Royal Collection Trust, said: "It was Prince Albert’s idea to have a balcony at Buckingham Palace, because he saw it as a way of enabling the royal family to connect with the people, and of course that's exactly how, in a sense, it continues to be used on important occasions."

She added: "But it began to be used very early on in Queen Victoria's reign, from 1851 waving off the troops to the Crimean War and welcoming them back on return."

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