Alan Ladd's character is the Black Knight. Throughout the film no-one seems to notice his armour is, in fact, white.
The scene in which the Druids make Lady Linet wear a blonde wig to be sacrificed was added because the stunt girl was blonde and her brunette wig wouldn't stay on.
Conspirators King Mark of Cornwall and Sir Palamides are both played by future "Doctor Who"s: Patrick Troughton would take the role on television in 1966-69, whilst Peter Cushing portrayed the big-screen version in two mid-'60s Dalek films.
For once, Alan Ladd's short stature, 5'6", made him the correct height for his action hero role, because the men of that period were much shorter than in modern times. This can be seen by the size of period armor displayed in museums.