The Duke of Edinburgh has been transferred to St Bartholomew’s Hospital for continued treatment, after 13 nights at another London hospital.

Prince Philip, 99, is being treated for an infection and doctors will also carry out 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.

Prince 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 at the time 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.

Prince Philip was transferred about three miles (5km) to St Bartholomew’s Hospital, also known as Bart’s, Uniformed officers from the City of London police were positioned at the hospital entrance.