The Princess of Wales has been pictured alongside Prince William leaving Windsor Castle today – just hours after she apologised for digitally editing a family portrait released on Mother’s Day.

The Prince of Wales was heading to Westminster Abbey for the annual Commonwealth Day service this afternoon with his wife beside him.

But rather than an extraordinary return to royal duties, MailOnline understands that Kate was heading to a private appointment instead.

It is not known where the Princess of Wales was going, but it was clearly on her husband’s route into central London because he arrived alone for the 2.45pm service attended by senior royals including Queen Camilla and Princess Anne.

Kate had looked out of her window as William appeared to read some notes on his phone as they were swept out of the grounds of Windsor Castle in a blue Range Rover that later dropped William at the Abbey without her.

The mother-of-three was not expected to be seen in public until after Easter following abdominal surgery and two weeks in a private London hospital in January. Her surprise appearance came as wild online conspiracy theories swirled around the princess and her health.

It came as Kensington Palace came under increasing pressure to release the original Mother’s Day photograph after the Princess of Wales apologised after she admitted she had edited the family portrait of herself sitting with Prince George, Princess Charlotte and Prince Louis.

Experts told MailOnline it was changed using Photoshop and related AI tools.

Prince William leaves Windsor for Westminster Abbey this afternoon with his wife the Princess of Wales next to him

Kate was seen looking out of the window of the car as William looked like he was reading notes on his phone

A smiling Prince William walks into the Commonwealth Service this afternoon

Queen Camilla and the Prince of Wales attend the annual Commonwealth Day Service at Westminster Abbey

Kensington Palace yesterday released the first picture of the Princess of Wales since surgery

Kate also posted the apology on the Prince and Princess of Wales’ Instagram account

The world’s major photo agencies later ‘𝓀𝒾𝓁𝓁ed’ the picture after noticing signs of digital editing, including a missing part of Princess Charlotte’s sleeve and the misaligned edge of her wrist and skirt, and the positioning of Kate’s zip.

This morning the Princess of Wales gave an apology on social media. She said: ‘Like many amateur photographers, I do occasionally experiment with editing. 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’. She signed it ‘C’ – for Catherine.

PR experts have described the Mother’s Day photo fiasco as a ‘massive own goal’ and urged royal officials to release the unedited picture in a bid to regain the public’s trust.

Kensington Palace had initially faced calls to reveal the truth behind the photo after the world’s top picture agencies – including the Press Association – ‘𝓀𝒾𝓁𝓁ed’ the image over claims it had been digitally manipulated.

Kate this morning admitted she had edited the photograph and issued a personal apology ‘for any confusion’ it had caused. Sky News’ analysis of the photo’s metadata found the image was taken with a Canon camera and was saved in Adobe Photoshop twice on an Apple Mac. Other experts suggested she may have used an AI tool.

The photo of the mother-of-three beaming with Prince George, Princess Charlotte and Prince Louis was the first official picture released of the princess since she under went ‘planned abdominal surgery’ in January.

While the princess publicly took the blame for altering the photo, Kensington Palace said it would not be reissuing the unedited photograph of Kate and her children.

PR expert Mark Borkowski said: ‘It’s plausible she’s at home playing with the computer and using an AI tool, but if they’re really going to regain any sort of trust they should release the unedited photo, it can’t be that bad if they just made a few tweaks.

‘I find they have risen to the challenge, provided the statement as an explanation – the question is with all the conspiracy theories running around, is whether people believe it and I’m not sure they will.’

Queen Camilla and the Prince of Wales attend the annual Commonwealth Day Service at Westminster Abbey

Queen Camilla and Prince William giggle as they walk the royals through the Abbey

Guests watch a video of King Charles delivering a message during the annual Commonwealth Day Service

Prince Edward and Princess Sophie are seen arriving at the Commonwealth Day service

Princess Anne smiles warmly as she enters Westminster Abbey

Birgitte, Duchess of Gloucester and Prince Richard, Duke of Gloucester, attend the Commonwealth Day Service

Geri Halliwell, 51, smiled at the cameras as she arrived at Westminster Abbey to take her seat

Deputy Prime Minister Oliver Dowden (L) and Britain’s Foreign Secretary David Cameron arrive

Mr Borkowski said the Mother’s Day photo had exposed a public relations problem for the monarchy: ‘That’s the issue, there doesn’t seem to be that much joined up strategic thinking at the heart of the Royal Family at the moment, which leads to these problems where it’s a very difficult organisation to manage in terms of PR.’

He added: ‘It’s a nightmare, even the softer stories of Edward turning 60 this week haven’t really resonated at all because no one’s interested in them, they’re interested in the stars they’re not interested in the supporting cast and that is a problem at the moment.

‘They are under pressure, massively under pressure, this is a massive own goal.’

Royal sources stressed this was ‘an amateur, family photograph taken by the Prince of Wales’. It’s understood it was taken in Windsor last week.

They said the couple wanted to offer an ‘informal’ picture of the family together for Mother’s Day and the princess made ‘minor adjustments’.

An aide added: ‘The Wales family spent Mother’s Day together and had a wonderful day.’

Sky News said an examination of the photo’s metadata revealed it was saved in Adobe Photoshop twice on an Apple Mac on Friday and Saturday and the picture was taken on a Canon 5D mark IV, which retails at £2,929.99 and used a Canon 50mm lens, priced at £1,629.99.

The first save was made at 9.54pm on Friday night and the second was at 9.39am on Saturday morning. It is not clear if the two saves were on the same device. The Palace has not offered any further clarification about the edits.