Buckingham Palace confirmed on Friday morning that Prince Philip had been admitted to the King Edward VII Hospital in London, for "oberservation and treatment" of an existing illness. The Palace have reported that the admission was planned, and the Duke of Edinburgh was not taken by ambulance.
An official statement from the Palace reads: "The Duke of Edinburgh travelled from Norfolk this morning [Friday 20 December, 2019] to the King Edward VII Hospital in London for observation and treatment in relation to a pre-existing condition. The admission is a precautionary measure, on the advice of His Royal Highness' Doctor."
Prince Philip, who is 98-years old, retired from his official public duties as a royal in 2017. Though he has made a significantly small number of official appearances over the past three years, he was most recently seen attending the wedding of Lady Gabriella Windsor in May earlier this year.