LONDON — Eating strawberries beside a memorial to Diana, Princess of Wales, two teenagers debated when it was that the princess had died. Was it in 2000? Or more recently?

The revelation that Diana died in 1997 – 20 years ago this week – took them by surprise. “That was before we were born!” said Floss Willcocks, 18, who is to start college this fall.

People in their late teens “don’t really know much about her,” added Ms. Willcocks’s companion, Caleb Barron, also 18. “She’s not really an icon for people our age.”

It was an exchange that highlighted a generational shift, a yawning gap in cultural assumptions and political aspirations between older and younger Britons that also showed itself in the vote on whether to leave the European Union.

After Diana was killed in a car crash in Paris two decades ago, she was mourned as a national hero. More than a million people lined the streets of London to watch her funeral cortege, while more than half of Britons watched it on television.

Lauded for her philanthropy, warmth and glamour throughout the 1990s — as well as for her traumatic divorce from Prince Charles, the heir to the British throne — Diana is still considered a symbol of her era for those old enough to remember her.