HMS Neptune was an ironclad turret ship originally designed and built in Britain for Brazil, but acquired for the Royal Navy in 1878.

Modifications to suit the Royal Navy took three years to complete and the ship did not begin her first commission until 1883 with the Channel Fleet.

[1] During the Russo-Turkish War of 1877–78 tensions dramatically escalated between Russia and Great Britain as the latter feared that the victorious Russian armies would occupy the Turkish capital of Constantinople, something that the British were not prepared to tolerate.

They mobilized much of the Royal Navy in case war did break out and purchased a number of ironclads under construction, including Independencia, in 1878.

[2] In British service she was deemed "a white elephant, being a thoroughly bad ship in most respects—unlucky, full of inherent faults and small vices, and at times a danger to her own consorts".

[3] Neptune proved a poor seakeeper as she was wet, difficult to manoeuvre and a heavy roller.

[5] Neptune had one 2-cylinder trunk steam engine, made by John Penn and Sons, driving a single 26-foot (7.9 m) propeller.

[6] Neptune was barque-rigged, but her twin funnels were so close to the mainmast that the sails and rigging rapidly deteriorated in service.

An armoured citadel 112 feet (34.1 m) long protected the bases of the gun turrets, the funnel uptakes and the ventilation shafts for the engines and boilers.

Neptune was provided with a conning tower protected by 6–8 inches of armour situated right in front of the foremast.

[10] HMS Neptune was laid down in 1873 for the Brazilian Navy under the name of Independencia by J & W Dudgeon in Cubitt Town, London.

A second attempt was made on 30 July during which the ship got about one-third down the slipway and stuck, extensively damaging her bottom plating.

[14] Independencia was run into by the British steamship Firebrick at Greenhithe, Kent on 23 February 1878 and sustained slight damage.

Neptune struck the training brig Sunflower anchored beside Racer a glancing blow and then hit the port side of HMS Victory, making a hole at her orlop deck.