The Duke of Edinburgh is undergoing testing and observation for a pre-existing heart condition after being transferred to another hospital, Buckingham Palace has said.
Philip, who is also being treated for an infection, is said to be “comfortable” after he was transported by ambulance from a private medical institution to St Bartholomew’s late on Monday morning.
The development will heighten concerns for the duke, who will turn 100 in June and has now spent his longest period in hospital – 13 nights.
But members of the royal family are expected to continue with their official programme of events and meetings this week.
Buckingham Palace said in a statement: “The Duke of Edinburgh was today transferred from King Edward VII’s Hospital to St Bartholomew’s Hospital where doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition.
“The duke remains comfortable and is responding to treatment but is expected to remain in hospital until at least the end of the week.”
Philip was shielded from public view as he left King Edward VII’s hospital in central London, where he had been receiving treatment for an infection.
Umbrellas were held up as he made his way into a waiting ambulance, at the rear of the hospital, and was taken to St Bartholomew’s Hospital in the City of London, near St Paul’s Cathedral.
The duke was initially admitted nearly two weeks ago on February 16 for a few days as a precautionary measure after feeling unwell. A week later, Buckingham Palace announced the Queen’s consort was being treated for an infection.
Philip is known for his “no fuss” attitude and to not suffer fools gladly, and Royal biographer Penny Junor said his demeanour in hospital would be important.
“Let’s hope he’s not resigned, let’s hope he’s not being a good patient because I think that would probably be a bad sign – a cantankerous duke is a healthy one,” she said.
The author highlighted how the Queen appeared at ease when she encouraged those who are vaccine hesitant to “think about other people rather than themselves” during a video call last week.
Ms Junor said: “I think the Queen looked very jolly in a message that she put out the other day about having the vaccine.
“She doesn’t look to me like someone who is desperately worried and waiting for the phone to ring.”
The duke received a visit from the Prince of Wales the first weekend he was in hospital and could be visited by other members of the family in the coming days.
Last Tuesday, when it was announced the duke would spend several more days in hospital being treated for the infection, the Earl of Wessex said he had talked to his father on the phone and he was “a lot better”.
Philip has been treated for heart problems in the past and in 2011 was rushed to hospital by helicopter from Sandringham after suffering chest pains as the royal family was preparing for Christmas.
In the serious health scare, he was treated for a blocked coronary artery at Papworth Hospital in Cambridgeshire and underwent a minimally invasive procedure of coronary stenting.
The Queen, their children and grandchildren visited during his four-night stay, which saw him spend Christmas and Boxing Day in hospital.
St Bartholomew’s is an internationally renowned hospital and Barts Heart Centre is Europe’s largest specialised cardiovascular service and a centre of excellence for both cardiac and cancer care.
Dr Charmaine Griffiths, chief executive at the British Heart Foundation, said: “We’re sorry to hear that our patron Prince Philip continues to be unwell and will remain in hospital for the time being.
“On behalf of everyone at the British Heart Foundation, I want to send HRH the Duke of Edinburgh and the rest of the Royal Family our very best wishes.”