The marriage of Princess Diana and Prince Charles was infamously troubled, and the couple separated in 1992 before divorcing in 1996. Their eldest son Prince William was only 10 years-old when they first split, and their separation was incredibly hard for him to deal with, especially in the years leading up to their divorce.

In his new book “Battle of Brothers: William and Harry – The Inside Story of a Family in Tumult,” Robert Lacey revealed that William’s grandmother Queen Elizabeth played a major role in getting him through this difficult time.

“It was then three years after his parents’ separation – just two years before Diana’s death – and the Queen was worried about William’s state of mind,” Lacey wrote in the book, according to Us Weekly. “The Queen actually feared that the boy might be heading for some sort of breakdown, she confided to one of her advisors – just as the prince’s mother herself had clearly cracked up mentally in several respects.”

He added that William’s grandfather Prince Philip “shared his wife’s concerns” and “suggested” that the Queen try to step in by “trying to get closer to this particular boy – who was not just her fragile grandson, but a future inheritor of her crown.” It was then that the Queen began her tradition of Sunday lunches with William, which “helped to turn the fragile schoolboy heading for a breakdown into quite a tough young man.”

William was very much comforted by his close bond with the Queen, who gave him a “moral compass and a purpose,” and he remains close to her to this day. Months after Prince Harry and his wife Meghan Markle stepped down as senior members of the British royal family, the Queen reportedly told William and his wife Kate Middleton “numerous times that they’re doing a wonderful job” as high-ranking royals.

“The wonderful thing about Kate and William is that they remain focused and calm even during their most challenging times,” a source said back in April. “She couldn’t be prouder. She takes pride in being on top of everything but recognizes that it’s time to hand off some responsibility.”