The ancient Mayans predicted the End of Days with uncanny precision: 21 December 2012.

But they also provided the key to staving off apocalypse: a flawless sapphire of incomparable beauty carved into the perfect likeness of a human skull.

For more than four centuries, the skull and its legacy of dark intrigue and murder have been hidden, protected by a code few can break.

Now it's about to be found.