An elderly woman is in a serious condition in hospital after a road accident involving the Duke and Duchess of Cambridge's police escort.
Prince William and Kate were travelling from London to Windsor when the woman, 83, was hurt on Monday.
The accident involved a marked police motorbike in the convoy, and the police watchdog is now investigating.
Kensington Palace said the royal couple were "deeply concerned and saddened" and had been in touch with the woman.
The woman - who is called Irene, according to the palace - was taken to hospital in a critical condition following the collision on Upper Richmond Road in Richmond, south-west London at about 12:50 BST on 17 June.
She is now in a serious but stable condition in hospital.
A Kensington Palace spokesperson said: "Their Royal Highnesses have sent their very best wishes to Irene and her family and will stay in touch throughout every stage of her recovery."
The duke and duchess are understood to have sent flowers to the woman.
The Independent Office for Police Conduct (IOPC) said it was investigating the circumstances of the collision after it was referred to them by the Metropolitan Police "in line with procedure".
An IOPC spokesman said: "Our staff attended the scene of the incident and after careful consideration, we have launched an independent investigation.
"The investigation is in its very early stages and the officer involved is assisting our inquiries as a witness.
"Our immediate thoughts are with the injured woman and her family and those affected by the incident."
Prince William and Kate were on their way to Windsor for the St George's Chapel service commemorating the Order of the Garter.
In January, the Duke of Edinburgh, 98, was involved in a car crash while driving near the Queen's Sandringham estate.
Prince Philip flipped his Land Rover Freelander after colliding with a Kia car as he pulled out on to the A149 in Norfolk.