“Forty years ago, on the morning of August 16 1972, Stefano Mariottini, a chemist from Rome on a scuba-diving holiday, was gliding through the waters of the Tyrrhenian Sea a few hundred yards off the coast of Calabria when he was startled to see, thrusting from the sea floor below him, what looked like a human arm. The deep south of Italy is just across the water from Sicily with its Mafia connections, and as signor Mariottini swam closer, he feared at first that he might have come upon the remains of a corpse.”