Earl Spencer's first wife, Victoria Lockwood, has spoken of the "hard and painful betrayal" she experienced after discovering about her then husband's post-marital affair.
In a revealing interview, the former model recalled the moment she discovered about the fling just six months after the birth of the couple's first child, Kitty.
Speaking to Hello! magazine, the 43-year-old, who now lives in Cape Town, South Africa, said: "It turned me overnight from a deeply contented, first-time mother to a hurt, scared and devastated woman."
The Earl, then Viscount Althorp, had conducted an affair with journalist Sally Ann Lasson following his 1989 wedding – a ceremony attended by the Prince and Princess of Wales, with Prince Harry as a pageboy.
Victoria overcame the heartbreak and the couple went on to have twins Eliza and Amelia in 1992, and Louis in 1994.
She had been battling with addictions to heroin and alcohol and also suffered with anorexia and bulimia, but she only began to confront her demons after Louis's arrival.
She said that her late sister-in-law, Princess Diana, was a great support during her marital problems.
She said: "I suppose Diana and I had quite a bit in common with our eating disorders and broken marriages, and she was compassionate."
The couple's marriage eventually collapsed after their move to South Africa in 1995 and when Kitty was seven they divorced acrimoniously.
A multimillion-pound divorce settlement was eventually agreed in their bitter divorce proceedings.
Kitty, now 17, told the magazine how her parents informed her of their divorce.
She said: "They told me that they didn't love one another any more, but that they still loved me. The positives of the situation were highlighted, such as two Christmases, two birthdays and two bedrooms."
The Earl has since remarried and divorced again, gaining two more children in the process.
Victoria, meanwhile, has been married for three years to Jonathan Aitken – unrelated to the disgraced former Conservative cabinet minister – and has a five-year-old son, Samuel, by him.
In her heyday Victoria was the face of Ralph Lauren, who once described her as "the most beautiful girl in the world".
Kitty expects to return to Britain this year and live with her father at the Althorp estate in Northamptonshire before starting university in 2009.
She said: "It will be great to live with my father again, although it will be tough to adapt to being away from my mother and siblings. But I'm excited by change and becoming more independent.
"I spend all my holidays at Althorp, and it is definitely my home. It represents my childhood and holds lots of special memories for me. Whenever I am there I feel relaxed and happy."
Kitty revealed she speaks to her father almost daily and said the criticism heaped on him in the national press has done nothing to dent her love for him.
She said: "It's hurtful for any daughter to read negative things about her father, but he's someone who remains true to himself.
"I am definitely a daddy's girl. I'm more like him than my mother. We share the same sense of humour and have similar interests."
She jokes that her background is so troubled it should feature on the Jerry Springer Show.
But she added: "From the outside, the structure looks so dysfunctional. However, every single member of my family is part of my happiness."
The full version of the revealing interview is in the latest edition of Hello!.