Earl Spencer after Diana's death in 1997, per People.

Lacey writes that during what were heated conversations about Diana's funeral, Charles made an "offensive" comment about the late princess. Diana's brother believed his nephews, William, then 15, and Harry, then 12, should not walk behind their mother's coffin, which anyone following that event then knows, did happen at the the funeral on September 6, 1997.

"Spencer felt quite sure that Diana would have been horrified at the idea of her sons having to endure such an ordeal," Lacey writes. "He had already told Charles as much." He added that one conversation, via phone call, "ended with the earl slamming down the phone on his brother-in-law after Charles had made a particularly offensive comment about Diana."

Lacey continues: "Prince Charles had no doubt that he should walk the long route with both his sons beside him. But Uncle Charles Spencer did not agree. He was already angry on his family's behalf that his sister’s funeral had been hijacked into a royal occasion, and he was particularly opposed to the idea that his young nephews should have to walk the best part of a mile behind their mother's coffin through the streets."

Now that Harry and William are adults, they've both been open about their mental health following their mother's death. During an interview with former soccer player Marvin Sordell in May, William and Sordell, who grew up without his father, discussed how loss affects mental health.

"When you've been through something traumatic in life, that is, your dad not being around, my mother dying when I was younger, your emotions come back in leaps and bounds because it's a very different phase of life, and there's no one there to kind of help you," William said.

In 2017, Harry spoke about the panic attacks he experienced following Diana's sudden death. "In my case, suit and tie, every single time I was in any room with loads of people, which is quite often, I was just pouring with sweat, like heart beating—boom, boom, boom, boom - and literally just like a washing machine,"he said, while discussing why he finally sought out therapy in his late 20s.

In a special World Mental Health Day interview with the podcast Teenager Therapythat published today, Harry and his wife, Meghan Markle, discussed the importance of self care.

"We all know what it feels like to have our feelings hurt. We all know what it feels like to be isolated or othered," Meghan said while sharing her own experience of internet trolling. Listen to the interview here.