With the support of Queen Elizabeth I (Flora Robson), English privateers such as Sir Francis Drake regularly capture Spanish merchantmen bringing gold from the New World.

Elizabeth is flattered by the young man's fervent devotion and later has an opportunity to take advantage of his offer of service when Hillary Vane (James Mason), an Englishman spying for Spain, is killed before the names of his English co-conspirators can be uncovered.

Michael, disguised as Vane, goes to the court of King Philip II of Spain (Raymond Massey) to get the letters that will set into motion a plan to assassinate Elizabeth.

Overwhelmed with shame, they agree to accompany Michael on a mission to deploy fire ships in a night attack on the Armada, massed off the coast of England.

With the working title of Glorianna, principal photography took place at Denham Studios, where a large water tank was used to launch the model ships representing the Spanish Armada and the English naval defenders.

[3] A portion of the film, including the beacons being lit on the English coast, and an armour-clad Queen Elizabeth giving her speech to the surrounding soldiers at Tilbury before the Battle of Gravelines, was used in the 1939 World War II propaganda documentary The Lion Has Wings.

"[4] Writing for The Spectator in 1937, Graham Greene gave the film a mixed review, acknowledging it as "well-directed and lavish", but criticizing its lack of historical realism.

Greene stated that "the sets are magnificent" and that "the acting is far better than we are accustomed to in English films", but considered the production to have "strayed out of history" and called certain scenes "absurd" and "embarrassing".