Kate Middleton stepped out to attend the National Portrait Gallery's Olympic-themed new exhibit in London wearing a stunning Stella McCartney royal blue dress and Prada pumps. But the real show-stopper of The Duchess of Cambridge's ensemble was the 18 karat yellow, rose and white gold diamond Trinity de Cartier necklace. The Olympics-inspired necklace features five rings and comes with the price tag of $78000. Next Thursday Kate Middleton and Prince William will receive the Olympic torch at Buckingham Palace as the famous flame makes its way to its final destination in Stratford, East London.