At the risk of cursing myself, my oxen and the fruits of my loins, I must give bad news to those who will crowd into the Hub in Edinburgh tomorrow to catch a glimpse of the Mitchell-Hedges Crystal Skull - supposedly a 3,600-year-old pre-Columbian relic with the power to hypnotise, or worse, anyone foolish enough to meet its chilling gaze.

It's a fake.

But, deep down, you knew that, didn't you? And it won't matter a bit. Because, like the Turin Shroud and Tony Curtis's toupee, some fakes are so celebrated that they become important cultural artefacts anyway. The Mitchell-Hedges Skull is exactly that. And its origins really are cloaked in mystery. So it's highly appropriate that it is starring in this weekend's Histories & Mysteries Conference, in a city that's full of both.

The skull was ostensibly discovered by Anna “Sammy” Mitchell-Hedges, the adopted daughter of a swashbuckling 1930s British adventurer called Frederick Alfred “Mike” Mitchell-Hedges. The pair claimed to be scrambling round an ancient Mayan city in what is now Belize when Sammy saw the skull - chiselled from quartz, and as big as a man's hand - glinting under a collapsed altar. Sammy dined off the story for the rest of her 100-year life (she died two years ago), even when it inconveniently emerged that her dad had in fact purchased the skull from an art dealer called Sidney Burney at a Sotheby's auction in 1943.

But where Burney acquired it, nobody knows. And since the usual scientific tests, such as carbon dating, don't work on quartz, the object still retains a few vestiges of the legend that the canny Mitchell-Hedges carefully wove around it: that it was a “skull of doom” imbued by Mayan priests with the supernatural capacity to heap disaster upon those who fail to pay it sufficient respect. Brrrrh! I can hear the Grim Reaper clunking up the stairs with my coffin even as I type this.

Mind you, it's not the only crystal skull on the block. There are 12 dotted round the world, mostly in private hands - though one is owned by the British Museum, and one by the Smithsonian in Washington. Experts have proved, at least to their own satisfaction, that the latter two are fakes, probably made within the past 200 years. There's no reason to believe that the Mitchell-Hedges bonce is any older.

But just as there are thousands of “Shroudies” who still maintain that the discoloured linen in Turin Cathedral once wrapped the crucified body of Christ, despite much scientific evidence to the contrary, so there are “Skullies” who continue to believe that the crystal skulls are ancient relics. There are 13 in all, they claim. And when the remaining one is discovered, the world will end. They even know the date: December 21, 2012. Pity it's not 2011. We could save ourselves the cost of hosting the Olympics.

Of course, cynics will point out that this first public display in Britain of the Mitchell-Hedges Skull comes, spookily, just a few days after the DVD release of Indiana Jones and the Kingdom of the Crystal Skull. A coincidence? Or evidence that, even in the realm of the paranormal, timing is everything.

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