Langdon Battery was built between 1898 and 1904 to mount three 9.2-inch Mark X BL guns, similar to Citadel Battery on the nearby Western Heights. The Battery also mounted two 6-inch Mark VII on CPII mount BL guns. This was the most powerful battery in Dover as this time with five BL guns, see TNA WO 78/5103. In about 1912 one of the 9.2-inch emplacements was adapted to take a 6-inch BL gun, thus changing the configuration to three 6-inch and one 9.2-inch guns.
A searchlight emplacement for two Defence Electric Lights was built close to the shore line in the cliff in front of the battery (see separate entry). The engine room was located on the cliff top with a guard house. There was a zig zag patch down to a tunnel which gave access to the two casemated electric light positions.
Between 10th September 1911 and 26th March 1912 a tunnel was built from the Eastern end of the battery out to the cliff edge to provide an observation post. The video below gives a view of the inside of this tunnel and observation position.