Fort Gilkicker was a Royal Commission Fort built between 1863 and 1871. The Fort was intended to support the Stoke By Lines and defend the beach and approaches to Portsmouth. The site of this new fort had previously been the Monckton Auxiliary Battery.
Fort Gilkicker was built with twenty two casemates on the first level, all facing towards the sea. There were an additional five guns to be placed on the roof of the casemates. The level below the casemates is for magazines and hoists. The gorge of the battery was protected by defensible barracks and a brick wall with dry ditch. During the building phase it was decided that all of the casemates and the emplacements on the roof would be protected by iron shields. It is believed that these iron shields were fitted after 1871 when the fort was armed with the following:
Casemates: Two 12.5-inch RML guns. Three 11-inch RML guns. Seventeen 10-inch RML guns. Rooftop: five 9-inch RML guns.
In 1888 some of the casemate guns were removed and the chambers filled with concrete to prove traverses for additional protection. By 1891 the Fort mounted ten 10-inch RML with five 9-inch RML on the roof.
In 1898 proposals were advanced to mount breech loading guns in Fort Gilkicker and in 1902 two 6-inch Mark VII BL guns and two 9.2-inch Mark X BL guns were mounted on the roof. This work was not completed until October 1906. At the time earth was placed against the old casemates, covering the old gun ports. In 1905 the Owen Committee indicated that these BL guns were superfluous to needs and they were removed by 1907.
During World War 2 the Fort was used by the Harbour Master and a large control and observation tower was built on the roof of the casemates.
The site has now be redeveloped a luxury flats.