HMS Sans Pareil was a Victoria-class battleship of the British Royal Navy of the Victorian era, her only sister ship being HMS Victoria.

HMS Sans Pareil

In deciding upon her design configuration the Board of Admiralty took what history shows was a retrograde step by requesting the reversion from barbettes to turrets for her main armament. She was completed slightly later than her sister-ship and was hence the last British battleship ever to be equipped with her main armament mounted in a single turret.

The choice of calibre, while influenced by the desire to mount as heavy guns as possible, was also influenced by the slow rate of production in the Woolwich yards of the 13.5-inch (340 mm) calibre guns mounted in most of the preceding Admiral class. HMS Benbow, of that class, mounted the heavier calibre guns for the same reason. Following on from this decision, and given that a turret is heavier than a barbette, it was not possible to mount the two guns separately in fore and aft positions and at the same time keep the ship within the displacement stipulated by the Board. Hence both were mounted in a single turret, placed forward of the superstructure. To provide a nominal fire to stern, a 10-inch (250 mm) gun was mounted aft of the superstructure, behind a light armour shield. This weapon fired a shell weighing 500 pounds with a muzzle velocity of 2,040 ft/s (620 m/s), and could in theory penetrate an iron plate of thickness of 20.4 inches (520 mm) at a range of 1,000 yards (910 m).

The Elswick yards also experienced delays in producing the gun of 16.25 inches (413 mm) calibre, so in fact the times between laying down and completion of the Admirals and of Sans Pareil were closely comparable.

Sans Pareil was the last battleship to be designed by Nathaniel Barnaby.

https://en.wikipedia.org/wiki/HMS_Sans_Pareil_(1887)