Princess Diana's tragic death on August 31, 1997 is being marked by a slew of TV specials.  And perhaps the most poignant one will be British ITV's documentary, Diana, Our Mother: Her Life and Legacy.

A sneak preview of the TV show features her sons, Princes William and Harry, speaking for the first time publicly about Diana in her role as a mother.

The two grown men recall she was a mischievous mom, who had an infectious zest for life, as the Telegraph reported.

The princes have stressed Diana's love of naughtiness and mischief in the doc, in which friends of the late blonde beauty also speak out.

In a clip, Harry, 32, whose relationship with Suits actress Meghan Markle, 35, has intrigued the world, said, "This is the first time that the two of us have ever spoken about her as a mother. She was our mum. She still is our mum.

"And of course, as a son I would say this, she was the best mum in the world. She smothered us with love, that's for sure."

William looked at a photo of Diana holding him while she was pregnant with Prince Harry and said to his brother, "Believe it or not, you and I are both in this photograph. You're in the tummy!"

William and Harry have admitted that they clammed up instead of talking to each other about their mother's death nearly 20 years ago.

Their dad Prince Charles and Di were officially divorced in 1996. People around the world were devastated when Diana died in a car accident the following year in Paris. She was just 36.