This battery is named after Field Marshall Robert Conelis, fist Baron Napier of Magdala, 1810-1890 and former Governor of Gibraltar.
The Battery was built over the Original 2nd and 3rd Rosia Batteries.
In 1868 Colonel Jervois recommended the building of a heavy RML gun battery in this area and between December 1878 and March 1884 a single 17.72-inch 100 ton RML was mounted here. Victoria Battery, at the location of the present Fire Station, was built at the same time with a similar gun. These massive RMLs were cumbersome to operate and using black powder were quickly obsolete.
In 1898 during training the barrel was split and it was decided to replace it with the gun barrel from Victoria Battery. This damaged barrel is believed to be buried near the current Fortress Headquarters (4th Rosia Battery) by Rosia Harbour.
The gun fired a a 2,000 pound projectile (910-kg) with either armour-piercing Palliser, High Explosive or Shrapnel shells. The projectiles were of three types, all weighing 2,000 pounds (910 kg) and having a diameter of 17.7 inches (450) mm:
Apart from Victoria Battery in Gibraltar, only two other 17.72-inch batteries were built, both of these in Malta. The Malta batteries were Rinella Battery and Cambridge Battery.
During World War 2 the site was used for a 3.7-inch anti-aircraft battery. The gun pit stretched across to Engineer Battery.
The British had only four 17.72-inch 100 ton guns and these were mounted at:
Gibraltar
Malta