The Duke of Edinburgh is being treated for an “infection” and is not expected to leave hospital for several days, Buckingham Palace has said.

Philip was admitted to King Edward VII’s Hospital in London last Tuesday evening as a precautionary measure after feeling unwell, and walked into the building unaided.

At the time Buckingham Palace did not disclose the reason for the 99-year-old duke’s admission to the private hospital, but have now revealed he is being treated for an infection and is “comfortable”.

Buckingham Palace said in a statement: “The Duke of Edinburgh remains at King Edward VII’s Hospital, where he is receiving medical attention for an infection.

“He is comfortable and responding to treatment but is not expected to leave hospital for several days.”

The Earl of Wessex said of his father in an interview with Sky News: “He’s a lot better, thank you very much indeed, and he’s looking forward to getting out, which is the most positive thing, so we keep our fingers crossed.”

Asked whether Philip was frustrated to be in hospital, Edward laughed and replied: “Just a bit. I think that gets to all of us, and then you can only watch the clock so many times and the walls are only so interesting.

“We’ve had some brilliant and lovely messages from all sorts of people and we really appreciate that and so does he, I’ve been passing them on. It’s fantastic, thank you.”