The searchlights at Alexandra Battery were an essential part of the Derwent Defence Network from 1890 until the Second World War.
Initially there was only one searchlight on Blinking Billy Point. This was designed to intercept the beam from the searchlight at the Queen's Battery so that the river could be lit up during a night attack.
The light from each lamp was enhanced by projectors that incorporated mirrors.
The engine that ran the searchlight was housed in a loopholed casement on Sandy Bay Road. In 1913 a second searchlight was installed on Blinking Billy Point - the position on the Queen's Battery was now redundant. After 1909 the searchlights on Alexandra Battery acted as the 'eyes' of the artillery based at Fort Nelson, built in that year.
With Federation in 1901 responsibility for defence had passed to the Federal Government, and the Volunteers were replaced by a reserve force. The men of the 36th Fortress Company Engineers were responsible for the searchlights.
On the night war was declared in 1939, 80 men of that Company were called from their beds to man the searchlights in case of invasion. The men spent 12 months in barracks on the hill behind the Battery before being posted elsewhere. Some were transferred to Fort Direction at South Arm, built during the Second World War. Others went overseas to fight, some did not return.