The Duke of Edinburgh has accompanied the Queen to a Guards Polo Club event, three days after being discharged from hospital for treatment for an infection.
The Queen's consort cut a relaxed and smiling figure as he watched a British Driving Society parade at Windsor Great Park in Berkshire.
After waving to well-wishers as he arrived at the event, the 96-year-old royal presented prizes to the winners of a carriage driving competition.
The Queen wore a mint green coat and matching hat at the event, which marked Prince Philip's first public appearance since he was admitted to a private London hospital on Tuesday evening as a precautionary measure.
During his two-night hospital stay, Buckingham Palace officials said the duke had cancelled an engagement at London Zoo as he continued to recuperate.
The duke was due to visit the attraction next Wednesday, in his role as an honorary fellow of the Zoological Society of London, to present the Prince Philip Award for Contributions to Zoology.
Buckingham Palace said there were no current plans for Philip to miss other royal engagements.