Sir Thomas Mallory wrote Le Morte D'Arthur between 1469-1470 while imprisoned. Though known for its tales of chivalry, Mallory had a criminal past involving theft, kidnapping and rape. The characters of King Arthur and the Knights of the Round Table were well-known in English legends by the 15th century, having originated from Welsh and French sources. Mallory's work collected these scattered stories into a single narrative and helped popularize the Arthurian legends.