Lady Diana Spencer and Charles, Prince of Wales, became engaged in February 1981. Her engagement ring consists of 14 solitaire diamonds surrounding a 12-carat oval blue Ceylon sapphire set in 18-karat white gold. It was created by jeweler Garrard and cost at the time, 28,000 pounds sterling. Diana's selection of this ring was unusual. It was neither custom-made nor unique and was, at the time of her engagement to Charles, featured in Garrard's jewellery collection and available to anyone for purchase. Some commentators say Diana selected it because it reminded her of her mother's engagement ring. Jewellery historian Leslie Field stated: "She [Diana] had obviously already said she would like a sapphire; she had half a dozen rings [to select from] and she chose this one purely because she liked it." Fields continued: "Somebody came up with the story that she immediately went for the biggest, but I asked her and she told me it definitely wasn't the biggest, she simply thought it was very beautiful."
After Diana's death, Princes William and Harry selected mementos from their mother's possessions. Harry chose the engagement ring, while William selected Diana's £19'000 yellow gold Cartier Tank Francaise watch. They eventually exchanged mementos. When Prince William proposed to Catherine Middleton in the fall of 2010, he gave her the ring. Middleton eventually had the ring resized. It was a size H, and prior to her wedding, she asked Crown Jewellers G Collins and Sons to attach two platinum studs to it to make it a size I.
The ring has a deep personal significance for Catherine, Duchess of Cambridge and her husband, Prince William, Duke of Cambridge. Prince William said at the time of his wedding, that the ring was very special to him and that giving it to Catherine was his way of making sure his mother didn't miss out on his wedding day.
After the engagement was announced, some called the ring the "Commoner's Sapphire," a reference to the bride's non-royal origins. Others considered the ring a tragic symbol associated with Diana's failed marriage to the Prince of Wales and untimely death in a car accident in Paris.