Was there a plot to kill Diana, Princess of Wales? As an inquest opens, there are many who believe the nature of her death was the latest in a long list of historic cover-ups.
Moments before her death, but was Diana deliberately killed?
Every day around the world, ordinary people are killed by the actions of drunk drivers. But could such a tragically common fate befall a princess?
As an investigation into the death of Diana, Princess of Wales opens in London on Tuesday, the events of 31 August, 1997 have become enshrined in conspiracy theory folklore.
For some, the death of Diana is up there with the alleged CIA plot to rub out president John F Kennedy or the US military's "cover-up" of the Roswell UFO landing in 1947.
The best, or most believable, conspiracy theories come with at least a modicum of "credible" evidence.
In the case of Diana, there is enough to seed doubt in some serious minds.
The Daily Mirror has used the opening of the inquest into her death to publish the identity of the person seemingly named by the princess herself as plotting to kill her.
In a letter apparently written by Diana and passed to her then butler, Paul Burrell, she appeared to foretell the manner of her death.
"___ is planning 'an accident' in my car, brake failure and serious head injury," reads the letter.
For years, Mohammed Al Fayed, whose son Dodi was killed in the crash with Diana, has claimed the pair were victims of a secret service plot to finish them off.
The lengthy French investigation into the deaths found simply that they were the hapless victims of their chauffeur's drunk driving. But questions still persist.
Was Diana pregnant by Dodi? Were they planning to marry? If so, would the ties between such a high-profile royal and a Muslim be unacceptable to the British establishment?
All these have been cited as "justifications" for Diana's death, just as JFK's alleged softening on Cuba and Vietnam are said, by some, to have willed his premature demise.
In the 40 years since his assassination, a mass of theories about Kennedy's death have ripened. Among the chief suspects is the CIA - the Central Intelligence Agency - which seems to have the dubious distinction of being implicated in more cover ups than anyone else.
One theory holds that the Titantic was torpedoed by a German U-boat
Over the years, the agency, an independent executive bureau of the US government, has been implicated in the deaths of Marilyn Monroe (for her affair with JFK); Bob Marley (for his fomentation of revolution in the Caribbean) and Dr Martin Luther King.
To some ears it sounds crazy, but given the CIA's incontestable links with other deaths - such as that of Che Guevara - others may wonder if it is all hokum.
Death and conspiracy theories are not destined to be always intertwined. One of the most celebrated cover-ups, if you believe it, is America's Apollo 11 mission to the moon.
Ever since Neil Armstrong uttered his historic words about "one small step" doubters have claimed the whole event was staged as a prime example of Cold War one-upmanship.
The argument goes that while an empty rocket was launched and crashed into the sea, Armstrong and co were ferried off to the Nevada desert to film TV sequences.
By way of evidence, they point out that no stars or shadows were seen in the background of the TV footage.
THEORIES IMPLICATING THE CIA
It planted Lockerbie bomb to frame Middle East nations
Was behind attempted assassination of Ronald Reagan in 1981
Serial killers are products of CIA mind control projects
The attraction of conspiracy theorising is obvious. It can help "make sense" of otherwise senseless acts; identifies a blame figure; and, if truth be told, adds bit of spice to the normally mundane explanations that seem to underpin so many historic news events.
Sadly for those who like to indulge in a little conspiracy theorising, the truth seems to be not so much out there, but here, now.
As Frederick Forsyth, a confessed conspiracy theoriser in many of his thriller novels, has said of the Diana-Dodi case: "It is high time the world adjudged the conspiracy theories to be what they are: as weird as they are offensive."