Tanya Rose was invited to the King's estate for a four-day visit by Prince Edward

The infamously strict Sandringham dress code has been laid bare by a PR chief who spent multiple days at the royal estate.

The remarkable glimpse into the formalities of royal life emerged from Tanya Rose, who as a teenager found herself navigating the exacting protocols of a stay at Sandringham. The founder of travel PR firm Mason Rose shared her recollections on Amanda Wakeley's Style DNA podcast.

Mrs Rose was just 14 when her Gordonstoun School friend Prince Edward extended an invitation to join the royals at their Norfolk estate shortly after Christmas in 1979.

She was the sole non-family member present during the four-day visit.

"Four long dresses, four outfits for breakfast, four outfits for tea, shooting things, Barbour, Wellington boots," she recalled when asked what was required for her stay.

"I didn't grow up like that, I did not have that wardrobe, so we had to go out and buy everything."

Among the items Mrs Rose brought along was a string of imitation pearls her mother had purchased from Fenwick, which held great sentimental value.

"My mother lent me the fake pearl necklace that she had bought at Fenwick; it was her pride and joy, and on the first night, I remember the Queen Mother saying to me: 'Is that a family heirloom?'" she recounted.

"Well, my mummy did give it to me," she told the Queen Mother, though she wisely omitted where she had bought it from.

That opening evening proved a daunting affair for Mrs Rose. When the gentlemen remained behind after dinner, the ladies withdrew to a separate room, leaving her in exclusively royal company.

"That first night, it was terrifying because I was the only non-family member, and the men stayed, and the ladies went into another room, so it was the Queen, the Queen Mother, Princess Margaret, Princess Anne and Lady Susan Hussey, who was the Queen's lady-in-waiting," she explained.

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Mrs Rose admitted she was "absolutely terrified" by the experience.

Yet the late Queen Elizabeth II swiftly recognised the teenager's discomfort and moved to ease it with characteristic grace.

Her approach was disarmingly personal and wonderfully human.

"The Queen was so divine because she knew I was nervous. I was absolutely terrified, so she started doing impressions of her groom, and just being so sweet to me. She was lovely," Mrs Rose said.

The visit was not without its embarrassments, however. During one dinner, Mrs Rose found herself seated between the then Prince of Wales and the Duke of Edinburgh — and committed a faux pas that did not escape notice.

"Everyone had a pot of coffee in front of them, and I wanted some sugar, and we all had a little salt thing in front of us, and I thought it was sugar," she explained.

Having spooned two measures of salt into her cup, the future King was quick to observe the mishap.

"Prince Charles said, 'What an extraordinary thing to do,' and I said 'Oh what,' and he said 'You just put salt in your coffee,'" she recalled.