King Charles has a 'constant battle' living with Queen Camilla

Their Majesties are based primarily at Clarence House in London, but also split their time between several other royal residences including Highgrove House in Gloucestershire and Birkhall in Scotland.

According to Elliott, King Charles and his wife are "polar opposites" in many ways, including when it comes to the temperature of their home.

Elliot revealed in Robert Hardman’s biography, King Charles: New King. New Court. The Inside Story, that King Charles loves his home to have a cold breeze running through it.

Meanwhile, Queen Camilla wants her living spaces to be incredibly "warm and cosy".

This leads to a "constant battle" between the King and Queen about having the windows open.

Elliot added: "There's a constant battle about it.

"He will have opened it. She will creep in behind and shut it.

"So there's a lot of: 'Oh, darling, you shut the window’, 'Yes, I have, because we're all freezing.' So a lot of banter goes on."

Elliot concluded that the King "usually wins on that front", but Queen Camilla "wins most other things".

The King’s sister-in-law is not the only extended family member to suggest Charles prefers his living spaces to be chilly.

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The monarch’s former Communications Secretary Julian Payne, previously wrote in The Sun that King Charles wanted the windows open in Scotland during winter.

He claimed: "The King dislikes being inside for too long and always has the windows wide open.

"A meeting at Birkhall, his home in the Highlands, in the middle of winter was not for the faint-hearted.

"I can remember more than one occasion when I thought I might have actually got frostbite while trying to write with a hand I could no longer feel."