Kate Middleton and Princess Diana: The Women in Prince William's Life

April 28, 2011 -- Engagement rings symbolize the love and commitment that encircles two people who have decided to join their lives forever. The ring Prince William gave Kate Middleton last November is bigger -- both in carats and symbolism.

It also symbolizes Diana -- its original owner -- and her importance to William.

This was visible from the beginning, when the two announced their engagement. "It's beautiful. I just hope that I look after it," Kate said.

"If she loses it, she's in very, very big trouble," William added.

He went on to tell reporters that the ring was his way of keeping his mother "sort of close to it all."

In this and so many other ways, she already is.

Watch the full story on 'Nightline' tonight at 11:35 p.m. ET

At first glance, Diana's and Kate's stories seem similar: two beautiful young women marrying into the royal family while the whole world watches. We remember Diana as the People's Princess -- glamorous, outspoken and compassionate -- qualities we see reflected in Kate.

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But perhaps it's in their differences that we see Diana's true legacy, and its role in her son's wedding and adult identity.

As a 19-year-old bride-to-be Diana was as much a girl as a lady. Though it may be hard to believe, she had met Prince Charles only a dozen times before they married.

The pressure of public life was almost too much to bear, according to ABC News royal correspondent Katie Nicholl.

"Diana's body language was very closed. You could see she wasn't very comfortable with the cameras," Nicholl said. "You'd see her looking down and allowing the fringe [of her hair] to cover her eyes, because she didn't want to be photographed."

Her tortured relationship with the press would last throughout her life, and she died trying to get away from the paparazzi. Few who watched her funeral will ever forget the image of her sons, Princes William and Harry, solemnly following her casket through the London streets.