It was Prince Harry's turn to hop on a horse yesterday when he played polo at England's Cirencester Park Polo Club. His older brother, William, participated in last week's Audi Polo Challenge in Chester. Both William and Harry traded their sportswear for suits on Saturday, though, when they joined Queen Elizabeth and Kate Middleton at the Epsom Derby, which also brought out Princesses Eugenie and Beatrice. Kate's sister wasn't able to join their family day, however — Pippa Middleton ran a triathlon instead! William and Harry will actually pit their riding skills against each other next weekend, as they're scheduled to compete against each other at a charity game for the Sentebale and Tusk Trust.charities.