The Duke of Edinburgh has spent a third night in hospital, where he remains under observation after being admitted on Tuesday (16 Feb).
Prince Philip, 99, was admitted to the King Edward VII Hospital in central London, on the advice of his doctor.
It is understood that the duke had been feeling unwell for a short period before the doctor was called and he was advised to go to the hospital. However, it was not an emergency admission and he travelled to the hospital by car.
A palace source has said he walked into the palace unaided and his condition is not related to Covid-19, although the exact reason for the admission remains undisclosed.
The palace said that the duke’s admission was “a precautionary measure”, on the advice of His Royal Highness’s doctor after beginning to feel unwell.
The Duke was previously said to be in “good spirits” and is expected to remain at the hospital for a few days of observation and rest.
The Queen, 94, has remained at Windsor Castle and continues to work as normal.
Prince Philip and the Queen have both been spending the recent lockdown in Windsor Castle with a small number of household staff. The couple received coronavirus vaccines from a household doctor in January.
The Queen performed her first face-to-face event of the year on Thursday (18 Feb), when she knighted a royal aide.
Vice-Admiral Sir Tony Johnstone-Burt was made Knight Commander of the Royal Victorian Order during a private and socially-distanced ceremony at Windsor.
Sir Tony runs a department that handles both official and private entertaining and hospitality across all royal residences.