At the height of the French Revolutionary War, a new alliance between France and Spain threatened to overturn British naval supremacy, upon which Britain's empire, economy and security depended. The key to British survival would be to prevent the French and Spanish navies joining forces - so when British Admiral Jervis encountered the main Spanish battle fleet off Cape St.Vincent, he decided to attack, even though outnumbered almost two-to-one. The battle would be decided by the daring actions of one British commander - Commodore Horatio Nelson - who would soon emerge as one of history's most brilliant naval tacticians.