The Duke of Edinburgh is "feeling better", his younger son said after visiting him in hospital.
Philip, 90, is suffering from a bladder infection and was taken to the King Edward VII Hospital in London from Windsor Castle on Monday as a precautionary measure.
The illness forced him to miss several events of the Queen's Diamond Jubilee celebrations, including a service of thanksgiving at St Paul's Cathedral.
The Earl and Countess of Wessex arrived at the hospital and stayed for just under half an hour.
As he left the hospital, Edward told reporters: "He is feeling a lot better, thank you very much indeed.
"So I think a good rest is probably what is required."
Asked if the Duke had been keeping up with the Jubilee celebrations, he said: "He's been watching it all on television but I couldn't possibly tell you what channel.
"But thank you very much for your attention. It's very much appreciated."
Asked how the Queen was doing without her husband, he said: "She's bearing up but missing him, obviously."
A Buckingham Palace spokeswoman said the Duke will remain in hospital under observation for a few days.