Royal insiders fear Kate Middleton’s Photoshop scandal is taking a toll on her recovery from the abdominal surgery which has sidelined her from royal duties — and made her health the focus of intense speculation.

The Princess of Wales looked strained as she sat next to Prince William Monday, gazing out of the window, prompting comparisons in royal circles to photos of her late mother-in-law, Princess Diana.

Kate, 42, has been hounded by rumors about the truth about her health since undergoing major surgery for a mystery condition in January.

The Prince and Princess of Wales showed the strain of their breaking marriage during a car journey during an official visit to Seoul, South Korea, in November 1992. They officially split a month s

Prince William and Kate were photographed Monday outside WIndsor Castle, the first time they had been seen together since Christmas amid speculation over her health.GoffPhotos.com

But they went into overdrive after she and Prince William posted a family photo on Instagram Sunday to celebrate British Mother’s Day, which turned out to be badly Photoshopped.

Kate took the blame herself Monday, apologizing and saying she had done the editing herself.

One well-placed royal source told Page Six, “It’s an awful lot to be under all of this public scrutiny when you are recovering from major surgery.

William joined his stepmother, Queen Camilla, at the Commonwealth Service after traveling to London with his wife Kate, who had a “private appointment”.Getty Images

“The rumor mill — particularly on social media — has gotten out of control, but Kate is recovering well and she will be back by Easter.

“She just needs to be left in peace.”

Another palace insider mused, “I worry about all this attention on Catherine. She did not look happy at all in the car on Monday.”

The insider added that it reminded them of photographs of Diana looking upset as she sat next to her former husband, King Charles, at the height of their marriage crisis.

Charles and Diana look away from each other at a memorial for the British Gloster Regiment in November 1992.AFP/Getty Images

One famous photo saw the couple sitting together on an official visit to Seoul, South Korea, in November 1992. the tension etched across their faces.

They announced their official split a month later.

Kensington Palace had stated that Kate would be expected back to public life at Easter after having her planned surgery and are continuing to stick to this while trying to quell rumors.

She was photographed last week near home in Windsor with her mother Carole Middleton behind the wheel, and then again on Monday with her husband en route to London.

The Mother’s Day photo that kicked off a photoshopping scandal. Kate poses with children, Prince George, Princess Charlotte and Prince Louis.Prince of Wales/Kensington Palac / MEGA

The world’s top photo agencies “𝓀𝒾𝓁𝓁ed” Kate’s photo amid a photoshop storm. Kate took responsibility for the editing blunder.AP

But while William, 41, was heading to the annual Commonwealth Service, Page Six was told that Kate was heading to a “private appointment.”

Global PR and marketing expert Mark Borkowski said the entire affair has shown up how the royal family fares when Kate, the “box office” attraction, is out of commission.

“It does focus on William’s decisions about how he calls the shots on how they manage the press… this shows a complete disengagement with the media.”

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Meanwhile, Kate missed another family event Tuesday when William joined mourners at the funeral of Thomas Kingston, the husband of his cousin Lady Gabriella Windsor.

The body of the financier, who was found dead last month aged 45, was carried in a procession that began at Kensington Palace, the family home of his widow, and ended at Ambassador’s Court at St James’s Palace.

A private family funeral was then held at the Chapel Royal. And while William was present, Kate remained at home.