The time around 500 A.D. truly represented the Dark Ages in England. The Romans had left Britannia, and the native Britons were dealing with an invasion of Angles and Saxons from mainland Europe. While the origins of the Arthur legend are obscure, the story is well known. Arthur, Merlin the Magician, Sir Lancelot, and Guinevere are familiar characters to most people, who know the story of the Knights of the Round Table. Arthur is generally thought to be a real person of this era, but no one really knows for sure.
Of course, while there's no concrete, verifiable record of Arthur or the other characters in this film, that doesn't matter; director John Boorman has created a movie that is magnificent in its scope, and vividly tells the Arthurian legend in entertaining style. The film pulls no punches in its portrayal of the brutal, difficult time of the late 5th and early 6th centuries. During battles, men didn't hide and shoot weapons at one another from cover, instead they clubbed and stabbed each other to death in hand-to-hand combat, resulting in bloody carnage on a massive scale. Boorman also has included some pretty steamy sex scenes, showing us that life during these times was not all bloodshed and battle.
The movie gives us colorful portrayals of Merlin, the sword Excalibur, the Lady in the Lake, and the ascent of the young Arthur. Eventually the Knights of the Round Table fall into disorganization and decay, only to be acquitted on the battlefield by an older Arthur and Lancelot, who find glory one final time. Long but never boring, bloody but realistic, "Excalibur" is simply enchanting and enthralling. Try to catch the widescreen version—you're cheating yourself otherwise.