James Beckett interviewed for Mordred.
Jan Waters interviewed for Guenevere.
Reg Whitehead was very seriously considered For Sir Paul.
In addition to actual Medieval castles in Spain used in this film, a castle was built on the back lot of Warner Brothers Studios for closer shots and direct storyline action. Long known at the studio as the "Camelot Castle" after filming ended, it was used in other films. In 1972, the Camelot Castle was renovated into a Tibetan Lamasery for the musical remake of Lost Horizon, and it was used extensively in the TV series Kung Fu. In the 1980's, the back lot castle was torn down to make room for an office building. Fortunately, the Alcazar de Segovia and the Coca Castle remain in Spain where they are both popular tourist attractions.
In later years, Richard Harris would buy the rights to the stage version of "Camelot" for $1 million, revamped the musical and took it on tour. This made him a very rich man.
In the original musical, Merlin is lured away from Camelot by the spirit of Nimue, who sings the song "Follow Me." Nimue was dropped from the film, and the song is sung by a chorus during the last of the scenes with Merlin.
Mordred has a song in the original musical called "The Seven Deadly virtues" that was eliminated from this film version.
Queen Guenevere's wedding dress was made of natural materials. The dress was made from fishing nets, the bodice had little seashells sewn on and on the train were hundreds of hand-sewn pumpkin seeds.
The knights' armor in the film was brought to Hollywood from Spain, where it had been used in El Cid. It was later rented to the Disney studio for Bedknobs and Broomsticks.
The song "If Ever I Would Leave You" won a Golden Globe Award for Best Original Song Written for a Motion Picture, even though it was not written especially for the film but for the original stage production of "Camelot", and all the other nominees were songs especially written for films. In addition Frederick Loewe won a Golden Globe for "Best Original Score", a score that he had actually written for the Broadway stage, not for films. This is the only instance in the history of the Golden Globe Awards that this has happened.
Two separate Medieval castles in Segovia, Spain, were used in this motion picture; one as Sir Lancelot's Castle in France and the other as Camelot itself in various long shots. The Alcazar de Segovia, with its mansard roofs and numerous turrets reminiscent of Disneyland's Sleeping Beauty's castle, was depicted as Sir Lancelot's home in Gaul (France)in this film. The opening and closing scenes were also filmed on the grounds of this same castle which may be seen in the background in the light of the approaching dawn. For Camelot itself, the Coca Castle, also in Segovia, was used in long shots and background shots to depict the towers and battlements of Arthur's legendary kingdom.