H.M.S. Neptune was one of that fascinating group of nineteenth century ships-of-the-line conceived and built in the age of sail but later converted to steam.
Designed as a classic three-decker to mount 120 guns, Neptune was laid down at Portsmouth in January 1827 and launched in September 1832. Measured at 2,694 tons, she was 205 feet in length with a 54 foot beam and, when fully manned, carried a crew of 1,000 officers and men. Completed in that long period of peace after the end of the French Wars, she saw very little active service except in the Baltic in 1854-55 and, in the late 1850s, was one of a number of obsolete three-deckers chosen for conversion to steam propulsion. Dry-docked at Portsmouth from August 1858 to March 1859, she was reduced to mounting 89 guns and fitted with a 2-cylinder single expansion 500nhp. engine and screw propeller which, on her trials, achieved a maximum speed of just over 11 knots under steam power alone.
After spending the remainder of 1859 on "particular service" in Home Waters, she was sent to join the Mediterranean Fleet in 1860 where she remained until paid off in 1862. Thereafter laid up in reserve, she was sold out of the service in 1875. Ironically, for a vessel which fired so few shots in anger during her forty year career, when she was in the Baltic in the mid-1850s, she was described as "an astonishing ship" by the fleet's hydrographer, who further stated that "she was one of the fastest and, with a regular, well-trained crew, was the crack ship [in the fleet]."