The Diana ring

When Prince William proposed to Kate Middleton in 2010 he opted to pop the question with a precious family heirloom that belonged to his late mother Princess Diana.

The beautiful 18 karat white gold ring featuring a 12 carat oval blue Ceylon sapphire stone surrounded by 14 solitaire diamonds was handpicked by Diana herself. When Prince Charles proposed to Diana, he presented her with a selection of rings to choose from, and she opted for the now-legendary sapphire stunner.

The Duke and Duchess of Cambridge met at St. Andrews University in Scotland, and legend has it that he first laid on his future wife when she walked down the runway at a charity fashion show held at the university. After asking Kate's father for permission, William proposed to her during a private holiday in Kenya.

When the engagement was announced, Prince William said the the ring was 'very special' to him, explaining that giving it to Kate was his way of making sure his mother 'didn't miss out'.

The couple's wedding, which was broadcast on television and online in more than 180 countries, was held at Westminster Abbey in London on April 29, 2011.

And while the ring was purchased for $40,000 in 1981, it is now estimated to be worth $430,000.