The Duchess of Cornwall has said the Duke of Edinburgh is "slightly improving" in hospital as Camilla carried out a visit to a community vaccination centre.
The Duke of Edinburgh is "slightly improving" but he "hurts at moments", the Duchess of Cornwall has said.
On a visit to south London, Camilla said of her 99-year-old father-in-law: "We keep our fingers crossed."
Philip, the nation's longest-serving consort, has spent 15 nights in hospital - his longest ever stay.
He is undergoing testing for a pre-existing heart condition and treatment for an infection.
The Duke of Edinburgh was transferred to another hospital by ambulance where he will undergo tests for a pre-existing heart condition.
Prince Philip, 99, was taken from King Edward VII's Hospital to St Bartholomew's Hospital at 11.15am on Monday.
Buckingham Palace said doctors would continue to treat him for an infection but would also "undertake testing and observation for a pre-existing heart condition".
The Duke was carefully shielded as he left the private King Edward VII hospital in London. Large umbrellas were used as a protective screen as he was transferred into a waiting ambulance.