Answer:
The story of King Arthur and his Knights of the Round Table is a legend, but it is thought that there may have been a tribal leader of Ancient Britons on whom King Arthur was based.
There was an excellent British TV series in the 60's called Arthur of the Britons (starring Oliver Tobias) which gave an idea of what that leader might have been like.
There is a Round Table hung up in The Castle, in Winchester, England, but this was actually constructed on the orders of Henry VIII.