Thousands of years ago, the story goes, a Persian Army 50,000 strong marched into Egypt. After stopping at an oasis, they marched on.....never to be heard from again.

Stories and legends had grown up around the disappearance; Herodotus reported that the army had been swallowed up by "columns of sand", but historians had been increasingly writing that off as one of early recorded history's many enigmatic riddles: too fanciful to be true, yet too tantalizing to entirely ignore.

Until now.

Archaeologists mindful of the legends had been periodically checking along a well-known caravan route, remembering that Troy had been regarded as little more than legend until Heinrich Schliemann [link] , stubbornly pursuing the city whose fall was chronicled in The Iliad, finally found its remains in the mid-20th century.

It turns out that the Persian Army in question had diverted from the caravan route for reasons unknown, taking instead a southerly route well-known at the time, but lesser known among modern achaeologists.

And it was there that the Castiglioni brothers hit pay dirt.