It was much easier to be an impostor in the ancient world, when travel was difficult, communications slow, and few people even knew what their rulers looked like. One of history’s oldest and strangest examples depended on this ignorance.

According to the Greek historian Herodotus, King Cambyses II of Persia became so jealous of his younger brother Bardiya, also known in history as Smerdis, that he ordered his assassination in 522 B.C. Imagine Cambyses’s shock, therefore, when news came to him while he was away fighting in Egypt that a man calling himself Smerdis had seized the throne.

ILLUSTRATION: THOMAS FUCHS

Cambyses died before he could confront the impostor. But Prince Darius, a former ally of Cambyses, suspected that the new king was actually a Magi priest named Gautama. Herodotus relates that Darius knew a crucial fact about Gautama: his ears had been cut off.

Royal etiquette kept the king at distance from everyone—even the queen lived and slept in separate quarters. But Darius persuaded her to find an opportunity to be in the king’s apartment when he was asleep and check his ears. They were missing! Darius promptly denounced this Smerdis as an impostor, proclaimed himself the savior of the kingdom and took the throne. Modern historians suspect that the real impostor was Darius and that he invented the Gautama story to justify his coup against Smerdis.

The Middle Ages were a boom time for royal impostors. Kings and crown princes were often assassinated or executed under conditions that could plausibly be spun into tales of miraculous escape. Some of those impersonating long-lost monarchs managed to get quite far. King Henry VII of England spent eight years fighting a rebellion led by Perkin Warbeck, who claimed to be one of the two princes held in the Tower of London and killed by King Richard III in the 1480s.

During the Renaissance, the most famous case in Europe involved neither a king nor the heir to a great fortune but a French peasant named Martin Guerre. In 1548, the feckless Guerre abandoned his wife, Bertrande, and their son. Eight years later, a look-alike named Arnaud du Thil suddenly appeared, claiming to be Guerre. He settled down and became a good member of the community—too good for those who had known the old Guerre. But Bertrande insisted he was the same man. The deception unraveled in 1560 when the real Martin Guerre made a sensational return in the middle of a court trial to decide du Thil’s identity. Du Thil was executed for impersonation, but the judge declared Bertrande innocent of adultery on the grounds that women are known to be very silly creatures and easily deceived.

Opportunities to claim titles and thrones diminished after the 18th century, and a new class of impostor arose: the confidence man. Mr. Santos isn’t yet a match for the Czech-American fraudster, “Count” Victor Lustig. In 1925, posing as a French government official, Lustig successfully auctioned off the Eiffel Tower. In Chicago the following year, he posed as an investor and swindled Al Capone out of $5000.