She and Prince William are keen to move on from the drama and put the focus back on their work.

William will be hoping to put speculation about his wife’s health behind him on Thursday when he is due to carry out two engagements in Sheffield linked to Homewards, his program to put six pilot locations on a path towards ending homelessness within five years.

The photo of Catherine posing with her children at home in Windsor for UK Mother’s Day had been intended to reassure the public that she was fit and well following several weeks out of the public eye as she recuperated from abdominal surgery.

It had the opposite effect, only serving to fuel conspiracy theories about her health and whereabouts.

“Like many amateur photographers, I do occasionally experiment with editing,” the princess said in a statement published on X.

“I wanted to express my apologies for any confusion the family photograph we shared yesterday caused. I hope everyone celebrating had a very happy Mother’s Day. C.”

Such is the level of curiosity about the princess’ health that The Sun reported on its front page that she had been spotted at a farm shop in Windsor.

The revelation that another of her photographs was edited to such an extent that a global agency has attached a warning note may prompt questions about her many other family portraits released to the media to mark special occasions.

Last week, US broadcaster CNN confirmed it was reviewing all photographs handed out by Kensington Palace.

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Phil Chetwynd, the global news director of Agence France-Presse, said Kensington Palace was no longer a “trusted source” and that the princess’ manipulation of the Mother’s Day photograph clearly violated the agency’s rules.

Noting that it was rare for agencies to “kill” an image, he said Agence France-Presse’s hand had been forced because the palace did not respond to requests for an explanation or to release the original image.

The family portrait of Queen Elizabeth depicts her on a green sofa in a cluttered sitting room at Balmoral, surrounded by 10 beaming children. Dressed in off-duty attire, she looks directly at the camera in a photograph taken only weeks before she died.

Her grandchildren Lady Louise Mountbatten-Windsor and James, Earl of Wessex, the children of the Duke and Duchess of Edinburgh, are standing at the back.

In front of them are Lena Tindall, the daughter of Mike and Zara Tindall; Prince George and Princess Charlotte, the two elder children of the Prince and Princess of Wales; Isla Phillips, the daughter of Peter Phillips; and Prince Louis, the youngest child of the Prince and Princess of Wales.

Seated to the monarch’s right is Mia Tindall, holding baby Lucas Tindall, while to her left is Savannah Phillips. The image, a rare informal snapshot of the family, was lauded when it was released.

Prince Archie and Princess Lilibet, the Duke and Duchess of Sussex’s children, were notable absentees. Living more than 8000 kilometres away in Montecito, California, the Sussexes were the only senior members of the family who did not fly to Scotland to spend time with the Queen that summer.

Getty is understood to be the only agency that retains the image in its library. Other news and picture agencies no longer hold it as it was released for use until December 2023.

A community note – a feature on social media platform X that allows users to add context to posts – has also been added to the image on Kensington Palace’s profile.

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It states: “This image appears to have been digitally altered to give the impression that everyone within it was present at the same time. It is not a photograph of a moment, rather a collage of moments put together to create an illusion of a photograph.”

There is no suggestion that the princess inserted anyone into the photograph.

Kensington Palace declined to comment.