Prince Charles and Princess Diana
Princess Diana's secret daughter conspiracy resurfaced. Pictured: Prince Charles and Princess Diana at Westminster Abbey, London, for a centenary service for the Royal College Of Music on Feb 28, 1982. Getty Images/Fox Photos

Princess Diana may have had a secret daughter, one conspiracy theory has claimed.

Nikki Black, a journalist of New Idea, reported about the late Princess of Wales' secret daughter. The claims were first published by US magazine Globe years ago. The Queen reportedly ordered Princess Diana to undergo a gynaecological test to establish her capability of bearing children before her engagement to Prince Charles was announced.

According to Michael Thornton of Daily Mail, there was a narrow basis of fact in the story. The People's Princess confirmed that she underwent a gynaecological examination. "I had to be checked out before they would let me marry him," she told a close friend Elsa, Lady Bowker.

In addition, it was true that the People's Princess had wanted a daughter. "Diana always wanted a girl, and she shared the joy of her colleagues and friends when their kids were born," Patrick Jephson, Princess Diana's former private secretary told People. "Both my daughters were born when I was working with Princess Diana, and she more than once said how lucky I was to have girls."

The outrageous stories claim that Princess Diana's eggs were harvested and fertilized with Prince Charles' sperm. When the tests came back and Princess Diana was deemed to be healthy, the embryos were ordered to be destroyed. However, a "rogue doctor" reportedly secretly held onto them and implanted them into his own wife.

According to the story, the baby was a girl and was named Sarah. She's reportedly Prince Charles and Princess Diana's firstborn. Sarah said that she attempted to trace the origin of the donated embryo to find out who she really was. However, she received a menacing message warning her to stop looking if she valued her life.

The whole story of Princess Diana and Prince Charles' secret baby began as fiction, but this has changed following the publication of Nancy E. Ryan's 2011 book, "The Disappearance of Olivia."

Ryan never met the late Princess of Wales, but was fascinated by the royal and in vitro baby. Her book emulated Princess Diana and conceived the story of Olivia being Princess Diana's secret daughter who lives in hiding for fear that her existence would pose a threat to the royal family.

"Despite the book clearly being a work of fiction, when it was published at the end of 2011, an astonishing media metamorphosis occurred. Almost overnight, the possibility of Diana having had a secret daughter ceased to be fantasy and began to be promoted as fact," Thornton wrote.

Alison Maloney, a journalist of The Sun, didn't believe the claims that Prince Charles and Princess Diana had a secret daughter. "But the suggestion that her eggs were harvested and a secret child born elsewhere is nothing less than bonkers," she wrote.