The duo were all smiles at Greenwich Park and happily took their seats to watch their cousin, Zara Phillips compete. They donned official Olympic regalia, white polo and navy Team GB blazer for Duchess and navy blue blazer emblazoned with Union Jack, Olympic rings and Team GB logo for Prince.

The royal granddaughter of the queen, a princess in all but name, since her mother Princess Anne famously eschewed the title for her kids, had the full support of her family while competing in the cross-country equestrian event.

Along with Duke and Duchess, Prince Harry, Princesses Beatrice and Eugenie, and Camilla, Duchess of Cornwall, and her mother Princess Anne were on hand to root on the royal as she made her way through the 3.5-mile, 28-obstacle course.

And Zara Phillips repaid the enthusiasm of her family, the selectors and a delirious 50,000-strong home crowd with a faultless and gutsy performance which helped lift the British team into second place, with one day to go, and raised her own position from 24th to tenth.

After supporting Zara Phillips, Duchess, wearing a dove grey dress by Roksanda Ilincic, arrived alone for the reception at the Royal Academy of Arts supported by Founders Forum.

Arriving at the evening event, held to celebrate the Government’s GREAT Campaign, Kate Middleton flashed a dazzling smile for photographers, before being greeted by Prime Minister David Cameron.

The Duchess is expected to watch as many as 15 Olympic events in the coming fortnight.