The Italians had started constructing a pair of battleships, Duillo and Danolo, equipped with four Armstrong 15 inch guns weighing 35 tons each. These were superior to the armament of any ship in the British Mediterranean Squadron, and Inflexible was designed as a counter to them.
Inflexible was to be equipped with four of the largest guns available, weighing 60 tons each. She was largely designed by William White and laid down at Portsmouth Dockyard on February 24 1874. In 1875, Armstrongs produced an even bigger, 16 inch, gun weighing 81 tons, and it was decided to modify the design of Inflexible to use these. The Italians responded by changing their design to take even larger 100 ton 17.7 inch guns. As these could not be fitted to Inflexible, examples were ordered by the British Government for the coastal defences around Gibraltar and Malta (where one can still be seen at Fort Rinnella).
She was also equipped with a ram - ramming was considered a practical means of sinking an enemy battleship at that time. The Italian Re d'Italia had been rammed and sunk by the Austrian flagship, Ferdinand Max, at the Battle of Lissa in 1866. This had started a vogue for ramming which persisted until the 1890's, and many naval officers even believed this was the most effective weapon a ship could have. This was less surprising than it might seem to modern eyes, because it was expected that naval battles would be fought at a range of only a couple of thousand metres. Rams turned out to be a handicap in the end, as several warships were accidently sunk by them - for example HMS Vanguard by HMS Iron Duke in 1875, and HMS Victoria by HMS Camperdown in 1893.
Inflexible was launched on April 27 1876. Later that year the previous, retired chief of naval construction, Edward Reed visited the Italian ships and subsequently questioned their stability if the unarmoured ends were flooded.
As Inflexible was of similar design he raised grave concerns about it too. Construction was halted on Inflexible (and two other smaller ships) whilst a hastily convened committee examined the design. They concluded that it would be hard for gunfire to completely flood the unarmoured but heavily compartmentalised and partially cork-filled ends. However if this was managed then the ship would just be stable, capsizing at about 30 degrees heel.
Work restarted on the ship in December 1877. The ship was commissioned in July 5 1881, under Captain Jackie Fisher, although she was not completed until October 18. She was then sent to join the Mediterranean squadron.
Her guns were muzzle loaded using hydraulic rams fitted outside of the two turrets underneath an armoured glacis. To reload the guns, their turret had be rotated and the guns lowered to align with the rams before the gunpowder and 1684 pound shell could be loaded. In addition to the huge guns, she was very heavily armoured, the bottom of the main belt being 24 inches thick and almost completely proof against any contemporary gun. This is still the thickest armour which has ever been applied to a Royal Navy ship.
Although she was propelled by coal fired steam-engines she was equipped with a full set of masts and rigging so that 18,500 square feet of sail could be deployed. This was to help exercise and train the crew as this area would hardly move the ship with less than 2 square feet per ton.
She was also the first Royal Navy ship to be completely lit by electricity, and the first to have underwater torpedo tubes. The ship was equipped with many other novelties including water tanks to dampen the roll (which turned out to be useless). Much of the ship was without natural illumination, and Fisher had different deck levels painted in contrasting colours to make it easier for crew members to find their way around the ship.
She returned to Portsmouth for a refit in 1885. The full rig was removed and replaced by simple masts carrying platforms quick firing guns and signal flags. She went back to the Mediterranean for three years 1890 before returning to Porstmouth as guard ship, and finally going into reserve in 1897. She was sold in 1903 at Chatham for scrap.