Camilla, Duchess of Cornwall, gave an update on Prince Philip's condition while speaking to vaccination centre volunteers in London.

She said that he was "slightly improving" and that "we keep our fingers crossed" for his speedy recovery.

It's the Duke of Edinburgh's third week in hospital and he is currently undergoing tests for a heart condition.

He was transferred by ambulance to St Bartholomew's hospital to continue treatment for an infection as well as undergo testing for the heart condition.

"The Duke of Edinburgh was today transferred from King Edward VII's Hospital to St Bartholomew's Hospital where doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition," Buckingham Palace said in a statement.

"The Duke remains comfortable and is responding to treatment but is expected to remain in hospital until at least the end of the week."

It's currently not known when he will be leaving hospital, as he was treated previously during Christmas in 2011 for a blocked coronary artery.