An estimated 60,000 equestrian fans headed to the Queen's Berkshire estate for the Royal Windsor Horse Show.
The duke and his team competed in three days of carriage events
But the Duke of Edinburgh, who turns 84 in June, failed to triumph in the carriage driving events, coming fifth out of six with his team.
The Queen opened private grounds at Windsor Castle for the first time for the four-day gala, ending on Sunday.
Highlights included the Shetland Pony Grand National and the Household Cavalry Best Turned Out Trooper awards.
Simon Brooks-Ward, show director, said: "The public is enthralled by the concept of a major sporting and social event in the private grounds of the castle."