They were intended for Continental boat trains between London (Victoria) and Dover harbour, but were also later used for express passenger work to the South-West of England.

Although the improved ”King Arthur" class 4-6-0 locomotives were capable of the heaviest express passenger work between London and South West England, there was a growth in demand for Continental traffic travelling via Dover and Folkestone.

These would require a more powerful locomotive, able to pull heavier loads at sustained speeds of 55 mph (89 km/h), so as not to impede the congested electrified lines around London.

[3][4][5] After examining the practice of other British railways, Richard Maunsell, the Chief Mechanical Engineer, secured agreement for a 4-cylinder design, with an improved boiler and Belpaire firebox.

[7] The prototype E850 named Lord Nelson was ordered from Eastleigh railway works in June 1925 but production proceeded slowly, at Maunsell's insistence, to ensure that the weight was kept to a minimum at every stage,[8] so the locomotive did not appear until August 1926.

It was tested on a variety of duties over the next year, with sufficiently encouraging results for an initial order for ten more locomotives for delivery between May 1928 and April 1929 to be placed.

However, during construction, it was decided to equip half of the class with 5,000 gallon 8-wheeled tenders necessary for the longer West of England routes and to allocate them to Nine Elms depot.

[citation needed] Maunsell was aware of the reputation for poor steaming enjoyed by the class and attempted to address it by the fitting of twin Kylchap blastpipes to No.

[citation needed] For a period after its introduction to the Southern Railway network, the Lord Nelson class held the title of "most powerful locomotive in Britain" – a claim based on its tractive effort.

[16] The class was gradually superseded on top link expresses during the 1940s by growing numbers of Bulleid Pacifics,[12] although throughout the 1950s they were frequently called upon during peak periods or to deputise for failures.

[22][page needed] The rebuilding of the Pacifics in the late 1950s and their subsequent increased reliability rendered the Lord Nelson surplus to operational requirements, and they were gradually phased out of service.

[24] After the war, the livery was reverted to the Southern Railway Malachite Green standard with "Sunshine Yellow" lining on the boiler rings.