The British Royal Navy built a series of pre-dreadnought battleships as part of a naval expansion programme that began with the Naval Defence Act 1889. These ships were characterised by a main battery of four heavy guns—typically 12-inch (305 mm) guns—in two twin mounts, a secondary armament that usually comprised 4.7-to-6-inch (120 to 150 mm) guns, and a high freeboard. Primarily concerned with maintaining its "two-power standard" of numerical superiority over the combined French and Russian fleets, the Royal Navy built or purchased a total of fifty-two battleships of this type prior to the 1906 completion of the revolutionary all-big-gun Dreadnought, which gave the pre-dreadnoughts their name. William Henry White served as the Director of Naval Construction from 1885 to 1902 and thus ove