Editing LSWR N15 class (section)

==Background==
Robert Urie completed his [[LSWR H15 class|H15&nbsp;class]] [[Mixed-traffic locomotive|mixed-traffic]] 4-6-0 design in 1913 and the prototype was built in August 1914. It showed a marked improvement in performance over [[Dugald Drummond]]'s [[LSWR T14 class]] 4-6-0 when tested on local and express passenger trains. The introduction of ten H15 engines into service coincided with the outbreak of the First World War, which prevented construction of further class members.

Despite the interruption caused by the conflict, Urie anticipated that peacetime increases in passenger traffic would necessitate longer trains from [[London]] to the south-west of England. Passenger loadings on the heavy boat trains to the [[London and South Western Railway]]'s (LSWR) ports of [[Portsmouth]], [[Weymouth, Dorset|Weymouth]] and [[Southampton]] had been increasing prior to the war, and was beginning to overcome the capabilities of the LSWR's passenger locomotive fleet.<ref name=Swift1>Swift, p. 9</ref> His response was to produce a modern, standard [[Inter-city rail|express passenger]] design similar to the H15.<ref name=Bradley41>Bradley (1987), p. 41</ref>