Prince Philip is reportedly struggling and looking visibly strained since his car crash at Sandringham earlier this month.
The Duke Of Edinburgh was left with minor injuries after his Land Rover crashed into a Kia on the A149 near the royal estate in Norfolk.
His 4×4 collided with the Kia, which was being driven by Emma Townsend, 28. Her nine-month-old daughter was unharmed but her passenger Emma Fairweather suffered a broken arm.
Prince Philip has since apologised but a source said: He has been visibly more frail since he was pulled from the wreck.
Prince Philip wrote her a letter saying: I would like you to know how very sorry I am for my part in the accident at the Babingley cross-roads.
I have been across that crossing any number of times and I know very well the amount of traffic that uses that main road.
It was a bright sunny day and at about three in the afternoon, the sun was low over the Wash.
In other words, the sun was shining low over the main road. In normal conditions I would have no difficulty in seeing traffic coming from the Dersingham direction, but I can only imagine that I failed to see the car coming, and I am very contrite about the consequences.
I was somewhat shaken after the accident, but I was greatly relieved that none of you were seriously injured.
As a crowd was beginning to gather, I was advised to return to Sandringham House by a local Police Officer. I have since learned that you suffered a broken arm. I am deeply sorry about this injury.
I wish you a speedy recovery from a very distressing experience.