King Arthur is really the stuff of legends. There probably was a real King Arthur somewhere in Britain, some time ago, but the story wasn't written until long after he was dead. By that time, writers were not particularly interested in keeping to the facts, if their story was to become popular. I guess not much has changed in a millennium and a half.
Excalibur (1981) is one of the better Sword and Sorcerer films. John Boorman (b. 1933) produced and directed it. Boorman was already famous for Deliverance (1972) and Exorcist II: The Heretic (1977).
The movie starred Nigel Terry (b. 1945) as Arthur. This was his second big film, after making The Lion in Winter in 1968. Terry was mostly unknown in the USA, as were most of the cast. Boorman was more interested in telling the story, rather than showcasing big stars. This leads us to an interesting start as Bit Actors for some new stars who would become famous.
Helen Mirren (b. 1945) was in Caligula (1979) and The Fiendish Plot of Fu Manchu (1980), but was still relatively unknown here. She plays Morgana (or Morgaine) the sorceress and it is interesting to see her in an early role. She is incredibly talented, and back then she was very pretty.
Nicol Williamson (b. 1936) was a bit better known after appearing in Robin and Marian and The Seven-Percent-Solution in 1976, and The Goodbye Girl the next year. Williamson was marvelous as Merlin who could walk on the mist.
Gabriel Byrne (b. 1950) played Uther Pendragon, Arthur's father, early in his career. Byrne went on to have over 80 titles on IMDb, and shared the lead with Kevin Spacey (b. 1959) in The Usual Suspects (1995).
Liam Neeson (b. 1952) shows up in his first big film. Neeson plays Gewain, a knight of the Round Table. No need to tell you what became of Neeson. (Oscar for Best Actor in 1994 for Schindler's List.)
Patrick Stewart (b. 1940) was well into his acting career, but not well known here. He plays Leondegrance, who would be Arthur's father-in-law, I believe. Stewart would appear in Dune in 1984, but not gain real notice in the states until he left for space in "Star Trek: The Next Generation" in 1987.
In some other roles we see Corin Redgrave (1939 - 2010) who was the brother of Lynn and Venessa. And director John Boorman's three children all appear in small roles, including his daughter Katrine Boorman (b. 1958) who played Igrayne (or Igraine), Arthur's mother.
Excalibur is a movie to see. It is dark and violent, but beautifully lush in the way it is filmed. It rained almost every day, so the greenery is particularly green. Maybe not one of my favorite films (and I have a long list) but it certainly belongs in my collection.