Two weeks later, the Royal Family's Instagram account posted another, similar picture of the Duchess, smiling as she met with students who had entered the Queen's Commonwealth Essay competition.
The top comments underneath the photo: "Diana Forever." "Long live the memory of Princess Diana!" "In a world full of Camillas, be a Diana." "Diana is still the real MVP." "Please stop forcing Camilla down our throats."
Indeed, even Charles and Camilla's own Clarence House Instagram account has been flooded in recent days with thousands of messages of support for the late Princess Diana.
What changed so rapidly? Netflix released season four of The Crown on November 15, with millions now glued to a season that examines, in large part, the implosion of Prince Charles' disastrous marriage to Princess Diana.
It's an excoriating portrayal, particularly for Charles (Josh O'Connor), who's depicted as a petulant, raging brat, entering into a marriage with a naive young woman 13 years his junior (Emma Corrin, magnetic as Diana) while still in love with Camilla (Emerald Fennell).
Through the season, Charles' initial frustrations with Diana turn to outright hostility. In contrast, the fragile, lonely young princess is shown making several desperate attempts to connect with her husband and save their marriage.
And as Diana's popularity among the public grows, Charles' attitude towards her ferments into a deep, raging resentment.
Throughout, Camilla is forever on the sidelines, his confidante and lover. Of course, The Crown is presenting a fictionalised account of a marriage – and affair – that was splashed across the headlines for years.
The Crown suggests Charles and Camilla's affair continued throughout his marriage to Diana — but real-life reports state Charles had virtually no contact with Camilla for the first five years of his marriage.
But it seems many viewers find it difficult to separate fact from fiction.
It couldn't have come at a worse time for Prince Charles: While his mother Queen Elizabeth II has no plans to abdicate the throne, she is now six months shy of her 95th birthday. Charles is waiting patiently in the wings for his time to ascend to the throne.
Me thinking about how Prince Charles & Camilla spent the last 30 odd years rebuilding their reputations and Season 4 of #TheCrown gets dropped in 2020 of all years pic.twitter.com/4sXnyqKgbM
Keenly aware he is nowhere near as popular as his mother, Charles and Camilla have worked hard to rebuild their image in the public eye for more than two decades as he prepares to take the throne – work that The Crown now threatens.
It's something the fictionalised Camilla notes in the final episode of this season of The Crown, as she and Charles debate whether he can escape his unhappy marriage to Diana and start a new life with her.
She does want to be with him, she insists, but, "I want to be humiliated and attacked even less. That's what'll happen if you put me in a popularity contest against her. I will lose: I'm an old woman, I'm a married woman, nowhere near as pretty, nowhere near as radiant. Someone like me has no place in the fairytale.
"She will always defeat me in the court of public opinion."
It seems that, 23 years after Diana's death and 15 years after Charles and Camilla finally wed, the court of public opinion is pitting the two women against each other once more.