An RAF rescue crew attempted to fly an unwell Duke of Edinburgh to hospital, but was thwarted by bad weather, the Ministry of Defence has said.
Prince Philip, 91, was taken to Aberdeen Royal Infirmary on Wednesday while staying with the Queen at her retreat at Balmoral after a recurrence of the bladder infection he had in the summer.
A Sea King helicopter was immediately dispatched to hurry him to the hospital but poor visibility and heavy rain meant the crew, who are used to working in difficult conditions, were unable to reach him.
"The weather was absolutely dreadful," a source said.
A Ministry of Defence spokesman said: "The RAF can confirm that a search and rescue crew from RAF Lossiemouth in Morayshire was asked to assist with the transfer of a patient. However, due to poor weather we were unable to assist."
The Sea King landed four times during the expedition, but could not get close enough.
The Duke made the journey of almost 50 miles from the castle in the Cairngorms to the city hospital by road in an ambulance instead. He has been advised to rest and so will have no visitors in hospital on Friday, sources have said. He is said to be in constant touch with his family by phone.
Philip is expected to remain in hospital for the next few days, but is said to be responding well to treatment. At the hospital, a police presence could be seen outside, with four officers standing guard.
His latest health scare came two and a half months after he spent five nights in hospital with a bladder infection following the Diamond Jubilee Pageant on the River Thames. He was forced to miss some of the key celebrations for his wife's 60 years on the throne after he was admitted to the King Edward VII Hospital in central London the day after braving the elements on a barge for several hours.
Philip also underwent a successful procedure to clear a blocked coronary artery last December and was in hospital for four nights over Christmas.