Thomas Malory had many sources to choose from when he began writing Le Morte d’Arthur. Although it is impossible to determine all of Malory's inspirations, there are a few major sources that most scholars consider as likely influences.
Already in existence were the Welsh tales of King Arthur. These fables heavily influenced Geoffrey of Monmouth when he wrote his epic Historia regum Britanniae (1137), which includes the characters of Merlin and Mordred, and also tells of Arthur’s defeat of Rome. Another author, Wace, translated Historia regum Britanniae into French, adding the Round Table into the lexicon of Arthurian literature. Wace's own work, Brut, is credited for engendering the popularity of and devotion to the Arthurian legends in France. Because of this popularity, many writers contributed to the Vulgate Cycle in the latter half of the 12th century. This cycle of stories includes the Grail Quest and the introduction of Sir Launcelot, among many other popular elements of the Arthurian legend. Malory admits within the narration of Le Morte d’Arthur that he draws heavily on the “French bookes” for inspiration.
It is important to note that although Malory was compiling an epic collection of Arthurian tales, he used significant discretion in ignoring some stories. Inconsistencies within the plot, character relationships, and timing of events support this assertion. Of all the stories within Le Morte d’Arthur, only the Tale of Sir Gareth is attributed solely to Malory's imagination.
Le Morte d’Arthur was reprinted and revised into several volumes over the years. Since Le Morte d’Arthur was the first major English compilation of Arthurian tales, it is held as the standard for all later English-language adaptations of the legend.
Its influences include the works of Shakespeare, Spenser, Twain, Tennyson, and Steinbeck. Contemporary authors who have adapted it include T.H. White, C.S. Lewis, Stephen King, Marion Zimmer Bradley, and Susan Cooper. It has also inspired many works in young adult literature.
In fact, Malory’s work has inspired adaptations across several genres including art, film, theater, and contemporary fiction. The Pre-Raphaelites were extremely influential in bringing King Arthur back into vogue during the 15th century, with works by artists such as John William Waterhouse, Sir Edward Burn-Jones, Dante Gabriel Rossetti, William Holman Hunt, and John Everett Millais, among others. Audrey Beardesly, of the Aesthetic Movement, produced a number of woodcuts specifically for a 1893 edition of Le Morte d’Arthur.
Several notable theatrical productions were produced in the latter half of the 20th century, including included Camelot, a 1960 musical adapted from T.H. White’s Once and Future King, itself adapted from Malory's work. The most recent theatrical adaptation was Broadway’s Spamalot, which is based off of the film Monty Python and the Holy Grail.
Films inspired by Le Morte d’Arthur include: A Connecticut Yankee in King Arthur’s Court (1949); Knights of the Round Table (1953); The Sword in the Stone (1963); Monty Python and the Holy Grail (1975); Excalibur (1981); and King Arthur (2004). The popular Mists of Avalon by Marion Zimmer Bradely was made into a TV miniseries in 2001. The British show Merlin and a recent American cable production called Camelot are re-imaginings of the original tales. The legends of King Arthur also extend into music, video games, comic books, and animated series. The stories of King Arthur and Camelot have infiltrated the cultural lexicon in such a way that not all these works can be directly attributed to Malory's epic, but we remain indebted to him for having consolidated the many legends into a mostly cohesive whole that preserved them for the ages.