"She'd love the children to bits, but she'd be an absolute nightmare."
In a new documentary for HBO, both Prince William and Prince Harry open up not only about royal life, but also about their treasured memories of the late Princess Diana.
In "Diana, Our Mother: Her Life and Legacy," William shared a particularly poignant and personal anecdote, telling viewers how he is “constantly talking about Granny Diana” to his two young children, Charlotte and George, in the hopes of keeping her memory alive.
"We've got more photos up 'round the house now of her and we talk about her a bit and stuff," he explained. "It's hard because obviously Catherine didn't know her, so she cannot really provide that… level of detail. So, I do regularly, [when] putting George or Charlotte to bed, talk about her and just try to remind them that there are two grandmothers — there were two grandmothers — in their lives. It's important that they know who she was and that she existed."
Though through his pain, William also showed a great deal of humor when discussing what he believes life would be like with his mother today.
“She'd be a nightmare grandmother, absolute nightmare," Prince William joked. "She'd love the children to bits, but she'd be an absolute nightmare. She'd come and go and she'd come in probably at bath time, cause an amazing… scene, bubbles everywhere, bathwater all over the place, and then leave."
William added that he believes much of his own parenting style was shaped by his mother’s hands-on style, saying he hopes to make “as much time and effort with Charlotte and George” as he possibly can, noting that he now sees what his own mother sacrificed for him and his younger brother along the way.
Beyond the HBO documentary, which can be streamed now, PEOPLE Magazine has also teamed up with ABC for an in-depth, two-night television event, "The Story of Diana," which will air on Aug. 9 and 10 at 9 p.m. ET, just shy of the 20th anniversary of her tragic death.
“One of the reasons I wanted to talk now is because I think after 20 years, somebody shifts from being a contemporary person to one of history, actually,” Charles Spencer, Diana’s brother, told PEOPLE. “And Diana deserves a place in history. This was a special person, and not just a beautiful one.”