The Duke of Edinburgh has been transferred to St Bartholomew’s Hospital for continued treatment, after 13 nights at another London hospital.
Doctors are treating Prince Philip, 99, for an infection. They will also undertake testing and observation for a pre-existing heart condition, Buckingham Palace said.
The duke is responding to treatment and “remains comfortable”, it added.
He is expected to remain in hospital until at least the end of the week.
Philip, who turns 100 in June, was taken to King Edward VII’s hospital in London on 16 February as a precaution after feeling unwell.
A palace source previously said the duke had walked into the hospital unaided.
On Monday morning, someone was screened from journalists’ cameras by umbrellas as they got into an ambulance outside the hospital in Marylebone.
The exact reason for Philip’s initial admission has not been disclosed, but his stay is not related to coronavirus.
Both the duke and the Queen, 94, received Covid-19 vaccinations last month.
The Prince of Wales visited his father for around 30 minutes the weekend after he was admitted.
Two days later the Duke of Cambridge said his grandfather was “OK” and that doctors were “keeping an eye” on him.
The following day, on 23 February, Buckingham Palace said Philip was being treated for an infection and was not expected to leave hospital for several days. The Earl of Wessex added his father was feeling “a lot better” and appreciated the “lovely messages” from the public.
