Prince William has said Princess Diana excelled at being a mother, but would have been an "absolute nightmare" as a grandmother.
The Duke of Cambridge has spoken publicly for the first time about the impact his mother's death had on him and his brother Harry in an ITV documentary marking the 20th anniversary of her passing.
He described his mother as a "joker" who "really enjoyed laughter and fun" and said the only time he ever saw her upset was when she was hounded by paparazzi.
Prince William, whose son George turned four yesterday (22 July), said he is constantly mentioning "Granny Diana" to his children. He said that he has put up pictures of his mother at home so that George and Charlotte learn about her.
"It's hard because obviously Catherine didn't know her, so she cannot really provide that level of detail," he said in the documentary.
"So I do regularly put George or Charlotte to bed, talk about her and just try and remind them that there are two grandmothers - there were two grandmothers - in their lives."
He added that his mother would love his two children "to bits", but would be an "absolute nightmare grandmother"
"She'd come and go and she'd come in probably at bath time, cause an amazing amount of scene, bubbles everywhere, bathwater all over the place and then leave," he said.
He also revealed in the documentary that Diana used to love embarrassing her sonsby sending them the "rudest cards you could imagine" while they were away at boarding school.
"I would be at school and I'd get a card from my mother. Usually she found something, you know, very embarrassing, you know, a very funny card, and then sort of wrote very nice stuff inside," he said.
The prince recalled how his mother once embarrassed him by inviting supermodels Naomi Campbell, Christy Turlington and Cindy Crawford to their house because she knew he was a big fan of the trio.
"I went bright red, and didn't know quite what to say and sort of fumbled and I think pretty much fell down the stairs on the way up. I was completely and utterly awestruck," he said.