She could not turn to Charles, whom she felt systematically undermined her, criticising her dress sense and how plump or how thin she was while making little secret of his enduring love for Camilla.
Her own parents offered no sanctuary - they had separated after a bitter divorce and could not begin to understand her anguish.
What became ever more apparent as I read her own words was her overwhelming longing for a loving family life - which she tried and failed to create with Charles and her two sons.
This, I think, explains so much about William's behaviour today, 20 years on from his mother's death, and the way he has been so incredibly protective of Kate.
It is the reason he has immersed himself in the Middleton family, breaking with royal precedent by spending so much time with his in-laws, Carole and Michael.
And it's why he locked himself away with Kate and his children in Norfolk safe from prying eyes and cherishing spending family time together.
I've been among Kate and William's harshest critics over the way they barricaded themselves behind the walls of their estate, avoiding public functions as the Queen and Prince Philip continue to perform their duties into their 90s.
I have questioned whether the Middletons are shameless social climbers, desperate for their children to "marry up".
Yet, to their immense credit, they offered Kate something Diana never had - a stable, loving family offering unconditional support to their children.
No wonder William was drawn to it. A mum like Carole could have made all the difference to Diana.
