An explosive biography of Princess Diana, published on this day in 1992, shook the British monarchy to its very core.

Diana: Her True Story shattered the royal fairy tale and made its author, Andrew Morton, a millionaire.

It also made him public enemy number one and, as the video above explains, marked the beginning of a royal crisis that the Queen later dubbed her 'annus horribilis'.

The book's many revelations were so outlandish that they were initially greeted with disbelief.

Indeed, only one newspaper - The Sunday Times - felt confident enough to serialise what seemed to be a collection of scurrilous allegations that had been fed to Morton by a number of unattributed sources.

The book portrayed the Princess of Wales - wife of a future king and mother of another - as seriously unstable, deeply depressed and bulimic.

Her marriage to the Prince of Wales was a sham, and this was due to the fact that Queen's eldest son - the heir to the throne - had been in long-term affair with his former girlfriend, Camilla Parker Bowles.

This loveless marriage had driven Diana to indulge in serious self-harm on no less than five occasions, beginning just six months after the world watched her getting married at St Paul's Cathedral.

[Read more: November 20, 1992 - Windsor Castle is devastated by fire]

Readers learned that she had flung herself down stairs at Sandringham, cut her wrists with a razor, cut her chest and thighs with a knife, thrown herself at a glass cabinet and cut herself with a lemon slicer.

These incident were "cries for help" rather than suicide attempts - or so claimed Morton's main, nameless source.

Debate raged across Britain over the accuracy of the allegations and the ethics of presenting rumour as fact.

But with smoke hanging in the air, the tabloids set about trying to locate the fire, and the marriage of Charles and Diana soon fell victim to a media feeding frenzy.

But no one was able to conjure up Morton's level of detail, and when Prince Charles eventually admitted to adultery, many began to suspect that Diana herself had recruited Morton to tell her side of the sorry story.

This he furiously denied - until, that is, August 1997.

Within a week of Diana's death, Morton revealed to a stunned world that the main source of his book was, indeed, Diana - and he had the tapes to prove it.

The startling revelation all but secured the book's status as perhaps the most significant biography in literary history.

Morton quickly updated his masterpiece, adding the interview transcripts in their entirety, and he duly returned to the top of the best-seller list.