Even though Britain led the world in steel production , the Royal Navy was slow to adopt steel warships . The Bessemer process for steel manufacture produced too many imperfections for large @-@ scale use on ships . French manufacturers used the Siemens @-@ Martin process to produce adequate steel , but British technology lagged behind . The first all @-@ steel warships built by the Royal Navy were the dispatch vessels Iris and Mercury , laid down in 1875 and 1876 .