Footage of Kate's public appearances shows that she has internalized this lesson.
"When you see Kate kneeling to talk to someone, it is very reminiscent of Diana -- throughout her life," Seward said.
Diana's death, from a car accident while her car was being chased by paparazzi, renewed William's childhood distrust of the media.
"William absolutely loathes the media," Seward said. "He is adamant that they are just scum. And you absolutely can't blame him. I mean, in his mind, and in Harry's mind, the media were the ones that killed his mum."
The tragedy provided a final lesson from Diana: Beware the paparazzi.
Last year, two French tabloids published topless photos of Kate. In his own departure from royal ways, William became the first senior member of the royal family to sue in a foreign court.
The case is ongoing, but William's message is clear: Respect the privacy of Duchess Kate and their soon-to-be-born child. Diana would be proud.