▁the ▁standards ▁of ▁the ▁time , ▁but ▁it ▁could ▁not ▁support ▁the ▁heav ier ▁guns ▁or ▁batter ies ▁of ▁art illery ▁required ▁to ▁tack le ▁enemy ▁war ships . ▁Instead , ▁two ▁new ▁gun ▁batter ies , ▁each ▁armed ▁with ▁five ▁ 3 6 - p ound er ▁( 1 6 . 3   kg ) ▁guns , ▁were ▁built ▁alongside ▁the ▁castle ▁in ▁ 1 7 9 5 , ▁with ▁a ▁further ▁eigh teen ▁ 9 - p ound er ▁( 4   kg ) ▁guns ▁mounted ▁in ▁the ▁old ▁fort ; ▁the ▁guns ▁concerned ▁had ▁all ▁been ▁captured ▁from ▁the ▁French . ▁▁ 1 9 th ▁century ▁▁ 1 8 0 0 – 5 8 ▁▁ ▁In ▁ 1 8 0 3 , ▁war ▁with ▁France ▁appeared ▁im min ent ▁once ▁again . ▁After ▁some ▁discuss ions , ▁it ▁was ▁agreed ▁to ▁adapt ▁the ▁ 1 6 th - century ▁keep ▁to ▁enable ▁it ▁to ▁hold ▁six ▁ 2 4 - p ound er ▁( 1 0 . 8   kg ) ▁guns ; ▁the ▁roof ▁was ▁v ault ed ▁and ▁a ▁central ▁stone ▁pill ar ▁was ▁installed ▁to ▁run ▁up ▁through ▁the ▁building , ▁work ▁estimated ▁at ▁the ▁time ▁to ▁be ▁likely ▁to ▁cost ▁£ 4 , 1 2 2 . ▁The ▁historian ▁Andrew ▁Sau nd ers ▁lik ens ▁the ▁resulting ▁building ▁to ▁the ▁various ▁Mart ello ▁to wers ▁being ▁constructed ▁along ▁the ▁south ▁coast ▁at ▁this ▁time . ▁It ▁was ▁proposed ▁to ▁build ▁two ▁temporary ▁gun ▁batter ies ▁to