Prince Philip had spent five nights in hospital where he was being treated with antibiotics, missing the final celebrations for the Queen's Diamond Jubilee.
As he appeared on the steps of the main entrance, the Prince waved to well-wishers and shook hands with staff.
When asked if he was feeling better, he nodded and quipped: “I wouldn’t be coming out otherwise.”
He is expected to celebrate his birthday privately on Sunday with the Queen and other members of the Royal Family at Windsor Castle.
As he appeared on the steps of the main entrance, the Prince waved to well-wishers and shook hands with staff.
When asked if he was feeling better, he nodded and quipped: “I wouldn’t be coming out otherwise.”
He is expected to celebrate his birthday privately on Sunday with the Queen and other members of the Royal Family at Windsor Castle.