Prince William and Kate Middleton are said to be “devastated” after a motorbike rider in their royal convoy knocked over an elderly widow in West London.

Irene Mayor, 83, is reportedly in a “critical but stable” condition after the  police motorbike outrider clearing traffic for William and Kate’s Range Rover hit her on Monday.

Witnesses said the bike was on the wrong side of the road when it hit Mrs Mayor, according to British newspaper The Mirror.

She was  “was thrown into the air and landed awkwardly”, said reports.

Mrs Mayor was taken to hospital by air ambulance with injuries that included a broken pelvis, according to reports.

The Cambridges were driving through Richmond en route to the Order of the Garter ceremony with motorbike escorts when the accident happened.

They apparently did not hear about the crash until they arrived at Windsor Castle for the Queen’s service, where they mingled with European royalty including Queen Letizia of Spain and Queen Maxima of the Netherlands.

Queen Maxima of the Netherland with Kate and Prince William at WIndsor Castle on June 17. Photo: Getty

“It is understood the Duke and Duchess of Cambridge were also devastated when told of the crash,” British newspaper The Sun said.

A statement issued by Buckingham Palace on behalf of the Cambridges said: “The Duke and Duchess of Cambridge were deeply concerned and saddened to hear about the accident on Monday afternoon.

“Their Royal Highnesses have sent their very best regards to Irene and her family and will stay in touch throughout every stage of her recovery.”

Kate, 37, and William, 36, reportedly sent get-well flowers and a handwritten note with a member of their staff, who visited the injured woman in hospital on Tuesday.

The palace spokeswoman said the royals would like to visit Mrs Mayor themselves in hospital if she was well enough.

“She’s got lots of injuries. They are just keeping her stable at the moment,” said her daughter Fiona, who lives with her mother in East Sheen, near the accident scene.

The Metropolitan Police confirmed the accident took place about 12.50pm on Monday.

Debris near the scene of Prince Philip’s January car accident. Photo: Getty

The crash comes months after Prince Philip, 98, surrendered his driver’s license after flipping his Land Rover in a collision with another car near the Queen’s Sandringham estate.

The Duke of Edinburgh later apologised to the other car’s passenger, who broke her wrist in the January crash.

Despite their concern for Mrs Mayor, the royals have pushed ahead with enjoying one of their favourite events of the year, Royal Ascot.

The race week kicked off on Tuesday, with the Queen, 93, beaming as she arrived for her family’s carriage procession with Queen Maxima and King Willem-Alexander of the Netherlands.

Queen Elizabeth and Queen Maxima greet crowds at Royal Ascot on June 18. Photo: Getty

Prince Harry and Meghan Markle were a no-show nearly six weeks after son Archie’s birth. But Kate and William spent the day laughing and checking form guides with family, including Prince Charles and the Duchess of Cornwall and Princess Eugenie.

Zara Tindall and an animated Kate caught up trackside. Photo: Getty

Meanwhile, the motorbike incident has been referred to the Independent Office for Police Conduct, the Buckingham Palace spokeswoman confirmed.