After his death, his body became one of the most sacred objects in history. Pilgrims, from the common man to the most powerful emperors, visited and knelt before the remains of their god-King. And then in the space of a generation, all trace of his tomb simply disappeared. What happened to Alexander’s body? Was it destroyed by a tsunami? Did Christians intent on stamping out all trace of other religions destroy it? Or, as one historian believes, does it still exist, renamed and venerated as a saint in one of the most glorious Christian basilicas in the world? With no archaeological evidence indicating the location of the lost tomb we are forced to examine ancient eyewitness accounts of people who visited the tomb and place it in Alexandria.

We reveal that despite the book suggesting he spent 20 years in the court of the Chinese emperor, there is no mention of Marco in Chinese records. Marco Polo’s last will and testament remains unsigned and even the inventory of his possessions made on his death has question marks hanging over it.Our experts examine all the best evidence. Did Marco Polo, or any European, travel so far into China so long ago? Are the famous tales really based on Marco Polo’s travels? And did a man named Marco Polo even exist?

Decades earlier, a popular writer in Mexico, Riva Palacio, was writing stories with a character called El Zorro, and a character called Guillen Lampart. Much of Palacio’s work was published in New York in 1908, where it could have partly inspired Johnston McCulley. Palacio’s fictional character of Lampart was based on meticulous research in to the real-life crime story of Guillen Lombardo from two hundred years earlier, when Mexico was a colony of Spain, and the Catholic world was in the grip of the Inquisition. Modern-day research in to the Inquisitions records reveals an intriguing fact; Lombardo was not Mexican, he was not even Spanish, he was Irish, and his real name was William Lamport. Posing as an aristocrat by day, Lamport was in fact a spy on a mission for the King of Spain. When he arrived in Mexico City he set about starting a revolution to liberate the local Indians from the tyranny of corrupt Spanish rulers. His actions got him arrested by the Inquisition who put him on trial, and from whose prison he made a breakout that would become legend. This programme examines the personal papers of Lamport, it reveals long-hidden reports from the Mexico archives, and investigates the daring prison escape, to open the Mystery Files on Zorro.

As well as producing electricity, the John Day Dam in Oregon is crucial for trade – but the lock is broken. Can Riley save the day?