The film is a historical drama set during the reign of Elizabeth I (Flora Robson), focusing on the English defeat of the Spanish Armada, whence the title. In 1588, relations between Spain and England are at the breaking point. With the support of Queen Elizabeth I, British sea raiders such as Sir Francis Drake regularly capture Spanish merchantmen bringing gold from the New World.
The Four Men of the title are British WWI veterans who decide to work secretly against enemies of the country. They aren't above a bit of murder or sabotage to serve their ends, but they consider themselves to be true patriots.
Before the war, a Fleet Air Arm pilot is dismissed for causing the death of a colleague. Working for a small Greek airline when the Germans invade Greece, he gets a chance to redeem himself and rejoin his old unit on a British carrier. This is regarded the last of the conventional, rather stiff 1930's style Ealing war films, to be succeeded by much more realism and better storytelling.
