Max Mumby/Indigo/Getty Kate Middleton wearing Princess Diana's sapphire engagement ring
The iconic ring that Prince William used to propose to Kate with in 2010 is well known as being the same one that Prince Charles gave to Diana, but the design of the piece dates back to the mid-19th century.
Garrard, who made the ring, was inspired by a piece of jewelry that Prince Albert commissioned for his bride-to-be, Queen Victoria, in 1840. The large sapphire surrounded by twelve round diamonds and set in gold was adored by Queen Victoria so much that she wore it on her wedding day as her "something blue" on her gown.
Over the next two decades, Queen Victoria wore the brooch often. When she died in 1901, she declared it an heirloom of the crown — therefore, it has been worn by every single Queen (and Queen Consort) since. That includes the current monarch Queen Elizabeth, who has also worn it numerous times over her lifetime, including prominent events such as Prince William's christening.
Indigo/Getty Queen Elizabeth wearing Queen Victoria's blue sapphire and diamond brooch
According to Garrard, Prince Charles picked a selection of their rings to be presented to Diana at Windsor Castle in preparation for the proposal. The collection included the bold sapphire and diamond ring because it reminded Charles of the brooch he had so often seen his grandmother and mother wear. Diana reportedly chose it as it matched her blue eyes, and the rest is history.
The iconic ring, which was not bespoke, features a 12-karat oval Ceylon sapphire set in 18-karat white gold and surrounded by 14 solitaire diamonds. It was valued at $37,500 in 1981 when Charles proposed to Diana, but it is now considered priceless because of its history.
Tim Graham Photo Library via Getty Images; Chris Jackson/Getty Images Kate Middleton and Princess Diana wearing the same engagement ring
During their official post-engagement interview, where Kate wore a royal blue dress by Issa that perfectly matched the ring, Prince William explained why the piece was so special to him.
"It's my mother's engagement ring so, I thought it was quite nice because obviously, she's not going to be around to share any of the fun and excitement of it all — this was my way of keeping her sort of close to it all," he said.
Chris Jackson/Getty Kate Middleton and Prince William on the day of their engagement
Sapphires have long been a go-to jewel for royal women, especially when it comes to marriage proposals. In addition to Kate and Diana, the Queen Mother had a blue sapphire engagement ring as does Princess Anne. Meanwhile, Princess Eugenie's engagement ring from Jack Brooksbank features a rare padparadscha sapphire, which is pink in color.