Fort Perch Rock was originally built between 1825 and 1829 to protect the mouth of Mersey and adjacent dockyards. By 1861 the armament of the Fort had been upgraded to:
Fort Perch Rock
Eight 32-pdr SB guns (original armament)
Two 7-inch RBL guns (new)
Eight 68-pdr SB guns (new)
By 1875 the old 68-pdr SB guns had been replace by 64-pdr RML guns. Presumably in the same emplacements.
In 1893 two Maxim machine guns were added to the armament and shortly later new emplacements for the Defence Electric Lights.
In 1897 three 6-inch Mark VI BL guns were mounted in the Fort, and in 1910 these were replaced by 6-inch, Mark VII guns.