As second-in-line to the throne, William’s role in the Firm is expected to become more involved. The prince follows in his father and grandmother’s footsteps and is known for his stoicism.
William tends to keep his emotions under wraps, but Ms Brown recalls a time when the Duke expressed them in a relatively unconventional way.
In an excerpt from her upcoming book ‘The Palace Papers: Inside the House of Windsor-The Truth and Turmoil’, published this week in Vanity Fair, Ms Brown recounted a story of the Duke keeping a photo of one of Diana, Princess of Wales’ love rivals on his dartboard at Eton.
She described a private lunch organised by Diana at Kensington Palace to which she invited Piers Morgan, who was the editor of the Daily Mirror newspaper at the time, and her eldest son Prince William.
Diana had recently been romantically involved with Will Carling, the captain of the England rugby team, whom she had met in 1995.
William became Diana’s closest confidante. (Image: Tim Graham Photo Library via Getty Images)
Mr Carling’s wife, Julia, revealed her husband’s affair with the princess, a move that Diana was reportedly “livid” about.
Ms Brown wrote that during her lunch with Mr Morgan, Diana said: “She’s milking it for all she’s worth, that woman.
“Honestly, I haven’t seen Will since June ’95.”
At this point, William revealed: “I keep a photo of Julia Carling on my dartboard at Eton.”
Julia and Will Carling were married for two years. (Image: Mathieu Polak/Sygma/Sygma via Getty Images)
Mr Morgan described the meeting in his diary and claimed that Diana allowed him to ask “literally anything”.
Of William, he noted: “He is clearly in the loop on most of her bizarre world and, in particular, the various men who come into it from time to time.”
Despite the Duke of Cambridge being in his early teens at the time, he became his mother’s “most trusted confidante”.
Ms Brown wrote: “William understood Diana more but idealized her less [than Prince Harry].
“He was privy to her volatile love life.
“He knew the tabloids made her life hell, but he also knew she colluded with them.
“By his early teens, he was his mother’s most trusted confidant.
“She used to describe him as “my little wise old man.”
However, William struggled with the publicity of his mother’s private life at school.
Ms Brown quoted historian Robert Lacey who said that William was “slumped on the sofa, his eyes red with tears,” following Diana’s bombshell 1995 interview with the BBC’s Martin Bashir.
Last year, it was confirmed that Mr Bashir manipulated Diana’s paranoia to obtain the interview.
He showed her brother, Earl Spencer, forged documents that “proved” her closest advisors had betrayed her to the palace.
Diana spoke to Mr Bashir in order to get her own side of the story out there.
Speaking on the matter, William said: “It is my view that the deceitful way the interview was obtained substantially influenced what my mother said.
Mr Bashir obtained the interview with Diana deceitfully. (Image: BBC)
“The interview was a major contribution to making my parents’ relationship worse and has since hurt countless others.
“It brings indescribable sadness to know that the BBC’s failures contributed significantly to her fear, paranoia and isolation that I remember from those final years with her.”
He described the interview as a “false narrative”.
The Palace Papers is written by Tina Brown and will be published by Century on April 26.