In September 1695, the Plymouth-born “king of pirates”, Henry Avery, seized treasure worth £600,000 (in today’s terms, nearly £100m) from the Grand Mughal fleet in the Red Sea. What happened next is uncertain. The most boring legend has Avery – AKA Henry Every or Long Ben – buried in a pauper’s grave in Barnstaple, Devon. Another, recently endorsed in the book Pirate Enlightenment by the late anthropologist and anarchist David Graeber, posits that Avery sailed for Madagascar where he established a pirate republic with his henchmen called Libertalia, a proto-communist utopia where all goods were held common. The National Maritime...