EXCLUSIVE: Princess Diana Was 'Scarred' by Father's Secret Second Marriage

Princess Diana is said to have been left "scarred" by her father's secret second marriage – and was so furious when she discovered the news she slapped him across the face, RadarOnline.com can reveal.

Diana's brother Charles Spencer, 62, makes the deeply personal claim in Swan Song, his account of his childhood with Diana and the extraordinary events surrounding her 1997 funeral.

Spencer writes that his sister was devastated after discovering through a newspaper that their father, John, had secretly married Raine McCorquodale, then Countess of Dartmouth, in 1976.

Spencer writes: "Diana was so disappointed and outraged by my father's secret marriage that she slapped him across the face – the only time she physically clashed with either parent."

Diana, who was 15 when her father remarried, is said to have acted on behalf of her siblings Sarah, Jane and Charles.

Spencer said Diana told their father: "That's for the pain you're causing us all."

The episode followed an already turbulent childhood for the future Princess of Wales. Diana was seven when her parents divorced after their marriage broke down, with the separation becoming an emotionally difficult period for the Spencer children.

John eventually received custody of the children.

His subsequent relationship with Raine, daughter of romance novelist Barbara Cartland, became another source of upheaval.

Spencer portrays his father's decision to marry without informing his children beforehand as a particularly painful betrayal for Diana, whose difficult relationship with her stepmother would continue into adulthood.

Swan Song has attracted huge attention partly because of Spencer's decision to disclose intensely private episodes involving Diana almost three decades after her death.

The book combines his memories of their childhood with his recollections of the days following Diana's death in a Paris car crash on August 31, 1997, at age 36, and the preparations for her funeral at Westminster Abbey.

Its publication also reopens questions surrounding how Diana's story should be told as the 30th anniversary of her death approaches, particularly when many of the people involved are either dead or unable to respond directly to Spencer's recollections.

Spencer has also become embroiled in a row with Piers Morgan after Swan Song wrongly linked the journalist turned broadcaster to the 1993 publication of intrusive gym photographs of Diana by the Sunday Mirror.

Spencer apologized for the "incorrect assumption," noting Morgan did not join the Daily Mirror until 1995. Morgan nevertheless said he intended to pursue legal action against Spencer.

The royal author has stressed he regards the memoir as his own account rather than an attempt to provide a definitive history of his sister.

In the introduction, he writes, "The aim of the book is to tell the truth about Diana from her brother's perspective."

The approach echoes the intensely personal intervention Spencer made at Diana's funeral, when his eulogy before a worldwide television audience became one of the defining moments following her death.

His address famously promised Diana's blood family would help protect her sons, Princes William and Harry, and criticized the pressures she had endured as one of the world's most photographed women.

Swan Song returns to the family relationships which shaped Diana long before she married the future King Charles III in 1981.

Explaining why he decided to revisit such sensitive memories, Spencer writes: "I thought, you know what?… I am going to tell things how I remember them, lay them down for good, once and for all."

Raine remained married to John until his death from a heart attack in 1992.

Despite years of hostility, Diana and her stepmother later reconciled, with Raine subsequently speaking warmly about the princess and their relationship before her own death in 2016, aged 87.

A source familiar with the Spencer family claimed to Radar: "Diana was scarred by what happened with her father. She had already experienced the breakup of her parents' marriage as a little girl, and then her father secretly marrying another woman added another layer of hurt and instability.

"Discovering something so important about your own family through a newspaper rather than hearing it from your father was enormously painful. For Diana, it wasn't simply that John had remarried – it was the secrecy and the feeling that the children had been excluded from something that would fundamentally change their lives.

"Her reaction shows the depth of that hurt. Diana striking her father was completely out of character in terms of her relationship with her parents, but she felt she was standing up not only for herself but for Sarah, Jane and Charles as well."

The insider claimed, "It left Diana with emotional scars. She wanted security, loyalty and a close family enormously, and experiences like this during her formative years inevitably shaped the way she thought about relationships and family life later on.

"Raine's arrival also created another deeply complicated relationship within a family that had already been through considerable upheaval.

"The Spencer children resented her intensely, and Diana carried much of that anger for years."

They added, "Charles' account makes clear that behind the privilege and grandeur of Althorp there was a family experiencing very ordinary human pain. Diana may have grown up surrounded by wealth and history, but that didn't protect her from feeling rejected or betrayed.

"The irony is that Diana and Raine eventually managed to find some peace with one another. But reconciliation later in life doesn't erase what Diana experienced as a teenager or how profoundly her father's secret marriage affected her at the time."