In this film, Vivien Leigh plays "Cynthia" a servant of Queen Elizabeth I, played by Flora Robson. In _Cleopatra (1945)_, Flora Robson plays a servant of Queen Cleopatra, played by Vivien Leigh.
It was while screening 'Fire Over England' that agent Myron Selznick saw Vivien Leigh and decided that she was Scarlett O'Hara. Coincidently she was in Hollywood to accompany her lover and future husband, Laurence Olivier who was making Wuthering Heights and Myron brought her down to the Gone with the Wind set, the Burning of Atlanta and introduced her to his brother David as his new Scarlett O'Hara.
Vivian Leigh and Laurence Olivier credit this movie as being the inspiration for their falling in love. Although both were married to other people, they became known as "the lovers" on the set.
When Korda re-released this film circa 1944, he commissioned a new trailer which implied that James Mason (by then a huge box office star for rival studio Gainsborough) was a major star of the film. In fact, Mason plays a tiny role in "Fire Over England" and his name does not even appear in the credits!