The Adventures of Sir Galahad (1949)

Sir Galahad is refused admission to King Arthur's Round Table until he regains the missing magic sword Excalibur, which makes its possessor invincible. Ulric, the Saxon King, invades England. Galahad, aided by Sir Bors, attempts to retrieve Excalibur from Bartog, Ulric's chief aide, who has gotten it from a mysterious knight.Merlin the Magician harasses Galahad at every turn, while Morgan le Fey, Arthur's sister and also a magician, helps Galahad fight both Merlin's magic and the Saxons. The Black Knight, a traitor within Camelot, is conspiring with the Saxons and a band of outlaws to overthrow King Arthur. When Queen Guinevere is seized by the traitors, Merlin relents and sends Galahad to the Lady of the Lake, who gives him Excalibur.