The Duke of Edinburgh has been involved in a car crash while driving near the Queen's Sandringham estate, Buckingham Palace has said.
Prince Philip, 97, was not injured in the accident, which happened as he drove a Land Rover out of a driveway onto the A149 shortly before 15:00 GMT.
The other car involved was a Kia. Two women in it needed hospital treatment - they have since been discharged.
Eyewitnesses said the duke's Land Rover overturned during the collision.
They said they helped the duke out of the vehicle. He was conscious but very, very shocked and shaken, they added.
Norfolk police said it was force policy to breath test drivers involved in collisions and both had provided negative readings.
The duke is back at Sandringham and has seen a doctor as a precaution.
A woman who drove past the crash scene - near Babingley, a small village north of King's Lynn in Norfolk - at around 15:40 said she saw an ambulance and "a heavy police presence".
"I was just going down the A149 … and saw a lot of blue flashing lights ahead," she said. "I saw a black, 4x4 type car on its side and me and my son were like 'oh my word, that doesn't look good'.
"Luckily it was just sort of on the side of the road, the road wasn't closed in any way.
"Obviously it looked quite smashed in. I'm quite amazed he [the duke] is okay actually."
Norfolk police confirmed officers were called to the scene shortly before 3pm after a Land Rover and a Kia were involved in a collision.
It had previously been reported the duke had been driving a Range Rover.
The driver of the Kia suffered cuts, while the passenger sustained an arm injury, police said. Both were treated at the Queen Elizabeth Hospital in King's Lynn.
A statement said the road remained open and both vehicles were recovered a short time later.
Nick Cobb, a long-time Babingley resident, was driving past with his 16-year-old daughter Emily at about 15:10 GMT when they spotted an overturned car about 100 yards from their house.
"The [Land Rover] was on its side on a private road.
"The other car was well into the hedge on the opposite side of the road.
"There was lots of debris in the road, lots of glass and lots of other cars, some police cars, some from the Sandringham Estate and about six ordinary looking cars that looked as though they had stopped to help.
"We only found out that it was the duke's car when we saw it on the news. The road was not blocked by the crash and was open when we came past."
The BBC's Nic Rigby, at the scene, says all that's left are pieces of broken glass and the remnants of a wing mirror.
It has been a chilly day, he adds, and there were small flurries of snow in parts of Norfolk, but nothing that troubled the county's roads.
The Queen and Prince Philip have been staying at the estate in Norfolk since Christmas.
The Archbishop of York, John Sentamu, tweeted a prayer in support to the duke, and later another one for the two other people involved in the accident.
Analysis: 'Surprise that the duke still drives'
By BBC royal correspondent Jonny Dymond
There will be several sharp intakes of breath over this accident.
The first will be over the good news - that the Duke escaped unscathed. A photo of what is believed to be the accident shows what looks like a Land Rover resting on its driver side, having turned or flipped as a result of the collision. That must have been some impact.
The duke was, a witness told the BBC, "very very shocked". But the Palace says the duke was not injured and did not need medical treatment.
The duke is five months short of his 98th birthday. By anyone's standards, getting away from an accident like that unhurt is pretty impressive.
There will be some surprise that the duke still drives himself on public roads. But he has always been fiercely independent, and would have resisted any suggestion that he be denied the right to drive himself.
And there will now be an investigation into the circumstances of the accident. It might be that the duke is about to be persuaded to give up the wheel.
Royal biographer Hugo Vickers told BBC News: "Any kind of car accident at the age of 97 is likely to produce shock.
"Some years ago he gave up flying planes long before he needed to because he was scared that if something happened there would be a lot of criticism.
"You know, why was he, at the age of 55, still flying a plane when he should have retired at 48 or something like that.
"So he does listen to these things - he's very, very sensible.
"If anyone's involved in a car accident, it's quite a frightening thing. If he thought that he'd lost concentration or something or he hadn't seen somebody he would realise he's not up to it anymore."
The president of the AA, Edmund King said high profile car crashes involving elderly drivers often spark calls for bans or restrictions on older drivers.
But he added: "If driving restrictions based on age and safety were introduced we would be more likely to restrict young drivers rather than older drivers.
"Young, predominantly male, drivers are much more likely to crash within six months of passing their test than older drivers within six months of hanging up their keys.
"Older drivers often self restrict their driving by not driving at night and only driving on familiar roads."
The duke famously drove the Obamas when the then-US president and first lady visited Windsor in 2016.
A discussion on whether to put average speed cameras on the stretch of the A149 where the duke's crash happened had already been planned by Norfolk County Council on Friday - prior to the crash.
Prince Philip retired from public life in August 2017 having spent decades supporting the Queen and attending events for his own charities and organisations.
Buckingham Palace calculated he had completed 22,219 solo engagements since 1952.
Since retiring from official solo duties, he has appeared in public alongside the Queen and other members of the royal family at events and church services.
He did not attend the Royal Family's Christmas Day service at Sandringham last month.