Is the 2004 film King Arthur actually a true story?

Answer 1

No, absolutely not. Although whatever historical basis there is to the Arthur legend is derived from the efforts of fifth and sixth century Roman Britons to defend themselves from Anglo-Saxon invaders, the specific events of that movie are pure Hollywood. The Saxons were a sea going people and came in their long boats to land on the southern and Easter coasts of what is now England. They never marched down from north of The Wall. The picts who lived in what is now Scotland did raid south of the wall but they seem to have been beaten back in the fifth century and then had their attention turned to fighting against the Scotti who were invading northern Britain from Ireland.