Samir Hussein, WireImage

Prince William has proposed to his longtime love Kate Middleton with the same 18-carat sapphire and diamond ring his late mother, Princess Diana, received before her ill-fated marriage to Prince Charles, he confirmed today.

Middleton was sporting the iconic ring, which coordinated perfectly with her electric blue, silk dress, when she made her first official appearance with her groom-to-be at St. James's Palace.

William's decision to give his longtime love his mother's ring during a proposal in Kenya last month is a gesture that will certainly be scrutinized for its romantic and emotional symbolism.

"It [the ring] was very special to me and Kate is very special to me, so it's good that they are together," the prince told journalists gathered at St. James's Palace today. "It was to make sure that my mother did not miss out on today." Aww!

The late Princess Diana chose the ring herself from a selection offered by Garrard Jewelers, the royal family's official jeweler for three centuries.

"The passing on of a piece of jewelry is a very intimate thing, especially in the case of Prince William," notes Ashley Mendel Fox, an estate jeweler with New York City-based Camilla Dietz Bergeron. "This ring was present at almost every significant moment of Diana's time as princess; her wedding to Prince Charles; important social events and personal moments with her children."

"Now when Kate wears that ring, those wonderful times will be present for Prince William and the fact that he shared that with Kate demonstrates that he wants her to be as much a part of his past as his future," says Mendel Fox.

Diana's ring choice, made after she accepted Prince Charles's 1981 proposal, was controversial, because the ring was not custom-made at her groom's direction. Tongues wagged when the British press reported it was for sale in Garrard's catalog for $65,000.

Still, Diana was said to have adored the ring, which featured the prominent oval sapphire surrounded by 14 diamonds. She continued to wear it after her scandalous divorce from the crown prince.

It has been widely reported that Prince William, who will succeed his father as Britain's king, specifically requested the ring from his mother's estate following her 1997 death in a Paris car crash.

Click here for a look back at William and Kate's almost decade-long romance.

In more royal wedding news, read about the ring Prince Albert of Monaco gave to fiancée Charlene Wittstock.

And check out the unusual ring Jessica Simpson received from fiancé Eric Johnson.