Hayne’s Cave Battery was initially a smoothbore battery in 1788. In 1902 a new battery of two 12 pounder quick fire guns was approved. The battery was built between 24th June 1902 and the 26th February 1904. The battery cost £2546, £46 over the estimate. Initially armed with two 12-pdr QF guns, it was rearmed with two 4-inch Quick Fire Guns on 5th January 1916.
The two gun emplacements are located on separate spurs some 100 metres apart, with the magazine to the rear some 50 metres away.
The original 12-pounder guns had apparently been removed to arm Merchant Vessels. The battery was intended to provide direct fire onto the South Mole and the entrance between this mole and the Detached Mole. To the rear of the battery underground magazines were built into the cliff face. These magazines remain in reasonable condition.
The A1 Gun Position (northern) was converted to mount a Bofors Anti-Aircraft position during WW2.
This whole area has recently been developed with a new suspension bridge running between the A1 and B1 guns. This allows for excellent viewing of the whole battery, but the underground works (casemates) are all sealed or backfilled.