Durable conspiracies: twenty years after Princess Diana's death

It has been two decades, and a stocktake of the conspiracy theories over the circumstances of Princess Diana's death in the Pont de l'Alma road Tunnel will reveal the same inventory as were spawned in the immediate aftermath of her demise. No response short of fanciful will do; no planned horror, however improbable, can be dismissed. Importantly, there must be some schema, a nefarious design intended to snatch away this figure's life.

The nature of myth has its own powers, its own resilience. Making the late princess into a myth served the ambitions of New Labour and the Blairite program, which promoted its own fictions through the dense web of spin and policy. "Call me Tony" Blair was a perfect accompaniment to the pop assemblage that was the People's Princess, confections of managed public relations.

The People's Princess still exerts a profane power from beyond the grave. She is still deemed "extraordinary" (a common mistake), and worthy of floral tributes outside Kensington Palace. An example of this wearisome nonsense is provided by Mara Klemich, visiting from Sydney: "We had never met her and been nowhere near her, but I think she touched so many people because of who she was, the way she conducted herself in the context of where she was living and who she became."

To be sustainable as a myth, it was necessary to develop, as Roland Barthes put it in his Mythologies, a set of meanings, essentially rendering them as natural, rather than crafted by the foibles of human intent. This compelling point leads us to conclude that looking at the myth is less significant than the story teller behind it. The show is nothing without its producer.

And my, were there stories to pick from, a vast pantheon teeming with variants as to how Diana died. One common conspiracy centres on a misunderstanding of causation. Goldie Lookin Chain, a Welsh rap outfit, would summarise this neat point in Guns Don't Kill People, Rappers Do. In the case of the princess, those with cameras did it, even if the ultimate responsibility should lie with a drunken driver and the poor choices made on the day on road safety.

The stubborn nexus with power – that the princess was somehow getting too big for her fancy boots – remains a noisy, if astonishingly misplaced theme. One can't make bricks without straw, as the expression goes, and straw was supplied at various intervals: in 2008 by former MI6 operative Richard Tomlinson, and then by former SAS sergeant, soldier N, in 2013.

Both figures were particularly keen to push the theory that Diana's driver had been blinded with lethally intended consequences. For Tomlinson, the suggestion of using a strobe light to blind a chauffeur was penned in an MI6 document from 1992 listing three methods of how best to kill Serbian leader Slobodan Milošević.

The mystery soldier N confided in his spouse about a flashing light deployed by a hit squad that distracted the driver at a crucial moment. Soldier N, we might say, was as pure as driven slush, arrested and detained along with SAS sniper Danny Nightingale in 2011 for having illegal weapons and ammunition. It did not take the Met long to dismiss his plagiarised account.

Mohamed Al-Fayed, whose son Dodi also perished with Diana, has been the most vigorous devotee of the conspiracy brand, blaming the Duke of Edinburgh. Here, the royal precedent to murder one's own returns to form.

For Al-Fayed, the design on the princess was simple: the couple would die at the hands of the security services because they had intended to marry. (Those seeking current grist for the mill suggest that the princess was intending to reject any marriage proposal – the old business goes on.)

The fuss kicked up by the grieving, somewhat unhinged father led to the stripping of Harrods' four warrants granting the store the right to declare its appointment by the Royal Family to supply goods. But hate sustains, and Al-Fayed busied himself with sniffing around the Duke of Edinburgh's alleged Nazi links. The world was spared witnessing the ex-Harrods owner's celluloid product claiming the same. Unfortunately, it has not been spared much else.

Each body of evidence has failed to convince the punters. The French Magistrates, for one, were never going to satisfy the Diana clan. (Their scepticism was fuelled by a good deal of anti-Gallic passion: if the Frogs did not do it, they certainly made it easier.)

"The vehicle's driver," concluded the 1999 report, "was in a state of drunkenness and under the undue influence of medication incompatible with alcohol, a state that prevented him from keeping control of his vehicle when he was driving at speed." Chauffeur Henri Paul hardly needed strobe lighting.

On the other side of the Channel, the Metropolitan Police's Operation Page revealed, after draining more resources, personnel and time, not to mention 800 pages, that "all the evidence at this time" pointed to "no conspiracy to murder any of the occupants in the car. This was a tragic accident." Instead of allaying doubts in December 2006, when it was released, there were those who refused to be convinced.

Nothing in terms of evidence would ever refute or repudiate the myth producing industry behind the princess. On the contrary, this steadfast refutation of evidence, the fanatical resolve to reject the empirical, provided a foretaste of that modern staple we now know as "fake news". The conspiracy complex was more Donald Trump than Donald Trump, and troublingly post-modern in turning all matters foundational and solid to dust. And in that dust is the grand sinister design.