King Arthur

Arthur was King of England in the 8th century, in Arthur's World, an alternate timeline.

Together with his knights and Merlin, Arthur battled the forces of Mordred and Morgaine, but was killed at the Battle of Camlann. Merlin, a future incarnation of the Doctor, placed Arthur's body and Excalibur in a dimension-crossing spaceship and hid it at the bottom of Lake Vortigern, near Carbury, in rural England. Legends sprang up that Arthur had survived the battle, albeit badly wounded, and would reawaken at the time of England's greatest need.

In the late 20th century, the Doctor and Ace discovered Arthur's spaceship and retrieved Excalibur. They later discovered that stories of Arthur's survival was just propaganda and that the King was really dead after all. (DW: Battlefield)

Other references

 * Arthur had a counterpart in the main timeline. (PDA: Wolfsbane)
 * Another version of Arthur existed in the distant future. (DWM: The Neutron Knights)
 * The people of Avalon believed that Merlin had brought Arthur to their world centuries ago. (MA: The Sorcerer's Apprentice)
 * On New Jupiter, the Medieval Zone of EarthWorld was influenced by legends of King Arthur. (EDA: EarthWorld)