Prince Charles reportedly has a panic room at his Highgrove House home, which is believed to be so strong it would survive even after a terrorist attack or airstrike.
The Prince of Wales installed the steel structure in his Gloucestershire home to protect himself and his wife Camilla should anyone ever manage to breach security and get inside the house.
Author Brian Hoey reveals details about the panic room in his book Not in Front of the Corgis, in which he suggests the structure of the panic room is so solid it wouldn’t break even if the rest of the house was destroyed.
He said: "It has been so built that even if the rest of the house is destroyed, it will drop intact to the ground floor".
The author claims the room is fully stocked with enough supplies to keep Charles, 72, and Camilla, 73, going for weeks should the need ever arise.
He added: "Inside are medical supplies, including containers of Charles and Camilla’s blood group, long-lasting food and drinks, an armoury, radio transmitters equipped to obtain a signal even within its steel walls, air purifiers and chemical lavatories."
Royal expert Ingrid Seward revealed in the documentary Secrets of the Royal Palaces that the room has never been used, however, former MP Rory Stewart was once accidentally locked inside after making a wrong turn.
The room was apparently installed after the heir to the British throne's great uncle Louis Mountbatten was killed by the IRA in 1979.
At the time, Charles realised he needed to be more aware of possible danger and built the room to protect himself and his then-wife Princess Diana along with their children Prince William and Prince Harry.
Royal expert Ken Wharfe and royal butler Grant Harold also said there was some concern over how visible the house itself was as well as how close it was to the main road.
"Anybody at that particular time could have scaled the fence or the brick wall," said Grant.
Charles was even able to move two footpaths that ran close to the home for security reasons in 1983.
In November 2002, intruders were stopped by bodyguards after being spotted on CCTV trying to enter the butlers' cottages on the edge of the grounds.
Then in 2007, alarms were triggered and sniffer dogs released after an intruder wielding a pitchfork broke into the estate.
In 1982, the Queen also had an encounter with an intruder when painter and decorator Michael Fagan somehow managed to make his way into her bedroom after scaling Buckingham Palace’s four-metre high wall. After pressing a panic button she was then thankfully able to stall him for long enough until security arrived.
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