 Originally Indefatigable was the only ship of the class , but Australia and New Zealand were later built as part of a scheme to improve the defense of the Dominions by having each Dominion purchase a ' fleet unit ' of one battlecruiser , three light cruisers and six destroyers . Only Australia fully acceded to the idea , forming the Royal Australian Navy , but New Zealand agreed to fund one battlecruiser . A modified Indefatigable design was chosen rather than the Lion @-@ class battlecruiser then building for the Royal Navy . 
