The LSWR N15 class was a British 2–cylinder 4-6-0 express passenger steam locomotive designed by Robert Urie. The class has a complex build history spanning three sub-classes and ten years of construction from 1918 to 1927.

The SR class LN or Lord Nelson class is a type of 4-cylinder 4-6-0 steam locomotive designed for the Southern Railway by Richard Maunsell in 1926. 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.

Hence the extensive rebuilding (and new construction) of 4-4-0 designs at a time when other lines were busily building Pacifics or heavy 4-6-0s. The ex-SER lines also had the problem of the narrow Mountfield and Wadhurst tunnels on the Hastings line , requiring locomotive and rolling stock rather narrower than permitted elsewhere.

After considering various options the eventual specification called for a four cylinder 4-6-0 locomotive with cranks set at 135 degrees, the drive divided between the first two coupled axles, 6 ft 7 in diameter driving wheels, a boiler pressure of 220 lb psi and a tractive effort of 33500 lb - the highest of any British express passenger ...

North British built N°767 Sir Valance heads a passenger train during Southern Railway days prior to the fitting of smoke deflectors. In the autumn of 1918 the LSWR's works at Eastleigh turned out the first three of a new express passenger 4-6-0 class designed by Robert Urie. A further seven appeared between February and November 1919.

His top express passenger locomotive for the range was planned to be a 4-cylinder 4-6-0 locomotive. This 4-6-0 was eventually to be called the Lord Nelson class and all were named after famous British Admirals. Short term requirements dictated that Maunsell first of all had to produce an improved version on the N15 design introduced by Urie in ...

Trials undertaken in 1914 with the H15 class prototype had demonstrated to Urie that the basic design showed considerable speed potential on the Western section of the LSWR from Basingstoke westwards, and could form the basis of a powerful new class of 4-6-0 express passenger locomotive with larger 6 ft 7 in driving wheels.

The LSWR N15 class was a British 2–cylinder 4-6-0 express passenger steam locomotive designed by Robert W. Urie. The class has a complex build history spanning three sub-classes and eight years of construction from 1918 to 1927. Following the grouping of railway companies in 1923, the LSWR...

The S15 was the third of Robert Urie's 4-6-0 designs for the LSWR. (the other two being the H15 and the N15). Twenty were built at Nine Elms in 1920. Their appearance is very similar the N15 class and they shared many components including the 180 lb per sq in boiler and tender designs.

The H15 class introduced by Urie in 1914 were possibly the first 4-6-0 mixed traffic locomotive to utilise Walschaert valve gear which had been developed by a young mechanic (Egide Walschaerts) designed it in 1844 whilst he was employed by the Belgian State Railway.