 Construction began in 1878 and though completed by 1882 the fort was operational in 1880 . Changes were made to the design during construction . Some forced by armament changes and others made to ensure additional security , including a rear @-@ defence wall and connecting road from Military Road . By January 1880 two guns were in place and the fort opened later the same year with an extensive opening ceremony on 2 October . In addition to parades , a small target was moored 3 @,@ 500 yards ( 3 @,@ 200 m ) offshore and fired on by all guns . A total of sixteen shots were fired during which one of the ten inch guns proved faulty . Only one ranging shot was fired and the shots were estimated to land from on @-@ target to 350 yards short . The fort 's final cost was approximately £ 36 @,@ 000 ( A $ 7 @.@ 05 million in 2005 ) consisting of £ 23 @,@ 600 for physical structures and the remainder for armament and fittings . At the time of its construction it was at the forefront of such fortification design , and was considered state of the art . 
