The Duke of Edinburgh is competing in a three-day event

The four-day gala is being held in the Queen's private grounds, with an attendance of 60,000 expected.

The Duke of Edinburgh, who turns 84 next month, is competing in the carriage driving events, which culminate on Sunday.

It is the first time the show has been hosted in the private area of the estate, after a move from Home Park.

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."

Other highlights of the weekend's programme include the Shetland Pony Grand National and the Household Cavalry Best Turned Out Trooper awards.