S15 4-6-0 LSWR Urie & Maunsell 30496 – 30515 & 30823 – 30847

S15 1.jpg

s15 2

Power Classification 6F
Introduced 1920 – 1936
Designer Urie and Maunsell
Company LSWR and SR
Weight – Loco 30496 – 30515  79t 16cwt

30823 – 30837  80t 14cwt

30838 – 30847  79t 5cwt

               Tender 30496 – 30503/30511 – 30515  57t 16cwt

30504 – 30510  44t 17cwt

30823 – 30832/30838 – 30847  56t 8cwt

30833 – 30837  42t 8cwt

Driving Wheels 5ft 7ins
Boiler Pressure 30496 – 30515  180psi superheated

30823 – 30847  200psi superheated

Cylinders 30496 – 30515 Outside – 21in x 28in

30823 – 30847 Outside – 20.5in x 28in

Tractive Effort 30496 – 30515 28,200lbf

30823 – 30847 29,855lbf

Valve Gear Walschaert (piston valve)

During the First World War, the London & South Western Railway (LSWR) management wished to address the requirement for a modern, standard heavy freight locomotive to work from London’s freight yards to the southwest of England. As the LSWR lacked existing freight designs capable of undertaking this task, a new design was needed to serve the south coast ports of Portsmouth, Weymouth and Southampton. The design was also to power traffic including milk trains, which required fast transit to the dairies in London. Robert Urie used this opportunity to develop his recent H15 class design further, applying the 4-6-0 locomotive concept to a purpose-built freight design built to order number S15. It was this order number that gave the class the name “S15”

 h15 H15 class introduced in 1914 by Urie. The locomotive was developed by Maunsell with four different groups of design completed by 1925.
 N15 N15 class as first introduced by Urie in 1918.
 s15 as new S15 class as originally introduced by Urie in 1920.

This was the third design by Robert Urie for the LSWR. It incorporated lessons learned from the operation of his H15 class, a design that was to provide the basis for future standardisation on the LSWR. To economise on maintenance, the S15 class had interchangeable components that could be used on a similar design, the N15 class passenger locomotive, which had the same overall appearance. Details such as the boiler, the two-cylinders and valve gear were standardised between the classes, although a taper boiler was used on the S15 and N15 classes, as opposed to the parallel boiler of the H15 class. The only other major difference was the smaller diameter of the driving wheels. Smaller diameter wheels gave better traction, essential for a fast freight locomotive.

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. The benefit of this system over the previously widely used Stephenson valve gear was that The Walschaerts valve gear enabled the driver to operate the steam engine in a continuous range of settings from maximum economy to maximum power. There were some earlier examples in Britain but Stephenson valve gear was still widely used when the S15 class were introduced.

30496-30515 were built at Eastleigh Works in 1920-1921 as the original S15 Urie design. They could be distinguished from the later locomotives by having the footplating raised over the cylinders, and were fitted with eight-wheel tenders. They were used primary for hauling express goods trains from Feltham yard, but were also used on passenger trains at up to 70mph at peak times. 30496-30499 were loaned to the GWR during the Second World War.

Urie retired as Locomotive Superintendent when the LSWR was amalgamated into the Southern Railway in 1923. Richard Maunsell was given the newly created post of CME to the Southern Railway, and decided to revise the cylinder arrangement of the locomotive. In doing so, he delayed the construction of further locomotives until the modifications had been made. When the modifications were trialled in service, it became evident amongst locomotive crews that Maunsell had taken a sound design and made it better, achieving a consistent locomotive capable of undertaking all the tasks for which it was intended. With the successful implementation of the modifications, permission was given by the management of the Southern Railway for a second batch of locomotives to be constructed.

30823-30832 were built at Eastleigh Works in 1927 to a design which Maunsell had developed from the original Urie design. They had had a higher boiler pressure, reduced diameter cylinders, smaller grates. The footplate was also modified for operation on the Southern’s new composite loading gauge, and differed from previous batches in having the Ashford-style cab, which was usually fitted to LBSCR locomotives. Unlike the original Drummond cab that was also favoured by Urie, the Ashford-style cab was of an all-steel construction and had a roof that was flush with the cab sides. It was inspired by the standard cab developed in 1904 by Deeley for the Midland Railway, and was one of a number of Midland features introduced by Maunsell’s chief draughtsman James Clayton, who transferred to Ashford Works in 1914 from the Midland Railway. Variants of this cab became standard for all new Southern Railway locomotives and converted Tank engines. They were fitted with eight-wheel tenders.

30833-30837 were built at Eastleigh Works in 1927and were fitted with smaller six-wheel tenders for working on the Central Section as the turntables found in that part of the network were shorter. The turntables were below standard size as a result of the London Brighton & South Coast Railway’s extensive use of large tank engines on both main passenger and freight duties. The larger tenders were used on the Southern Region as there were no water troughs on any of the routes.

From new, the rest of the class was equipped with the Urie 5,000-imperial-gallon eight-wheel bogie tender, which allowed the class to operate on the extended freight routes of the Southern Railway’s Western section. The standardisation measures undertaken by both Urie and Maunsell were soon vindicated by the fact that tenders and other parts were swapped with those of other classes on the Southern Railway when locomotives were under overhaul.

30838-30847 were introduced in 1936 having been built at Eastleigh Works. They had detail differences, reduced weight and a modified tender design and were fitted with eight-wheel tenders. A final modification was also applied to the class at this time, when all locomotives were equipped with smoke deflectors to improve visibility from the footplate when travelling at speed. This modification was a feature that became common to most Maunsell-influenced designs.

After modification by Maunsell, the S15 class was regarded by locomotive crews as an excellent goods engine best known for working heavy night express goods trains between Exeter, Southampton and Nine Elms. The S15s were also very capable passenger engines, being able to deputise in situations where there was a shortage of passenger locomotives during peak holiday periods. Both Urie and Maunsell S15s spent most of their working lives on the Southern Railway’s Western section, although they were sometimes used on inter-regional freights. In order to increase maintenance efficiency, all Urie S15 locomotives (which had the lower boiler pressure) were concentrated at the Southern Railway’s London freight depot at Feltham. This yard also featured the Maunsell S15s, which were allocated to Exemouth Junction, Hither Green and Salisbury, demonstrating the “go anywhere” nature of the class.

Despite the design being only a year newer, the S15s outlasted their N15 King Arthur class counterparts because of their dual freight/passenger abilities, though they were retired between 1962 and 1966 as part of the British Railways Modernisation Plan. Maunsell S15 number 30837 became the final member of the class in operation, returning to Feltham in January 1966 to work a farewell rail tour.

Number in Service.

Built Withdrawals No. in Service
BR Numbers Quantity
1920 30497-509



1921 30496





1927 30823-36



1936 30837-47

















  • Apart from when 3 locomotives of the first 20 produced were based at Nine Elms, from May 1948 until January 1950, they spent all of their working life under BR ownership based at Feltham. 30823-32 were based mainly at Exmouth Junction and Salisbury whilst 30833-47 were more widely distributed. Whilst these later engines were mainly based at Feltham some of them did have periods at other depots including Redhill, Eastleigh, Salisbury and Exmouth Junction.
  • Of the last 6 locomotives withdrawn in 1965, 4 were from the batch built in 1936 and 2 from those completed in 1927.


Allocation of locomotives in service with BR as at 1st of January.

1948 1952 1956 1960 1961 1962


4 3 0 0




2 7 3 4




9 10 6 4


Bricklayers Arms


3 3 0 0


Dover Marine


13 6 0 0




10 13 12 10


Exmouth Junction


0 0 0 0




0 0 4 0


Higher Green


1 2 0 0


Nine Elms


11 10 3 1




9 7 7 7


Stewarts Lane


12 8 0 0


74 74 69 35 26


  • Initial allocations for the earlier locomotives when new were:-
    • 30448-30457 were allocated to the West of England mainly at Salisbury and Exmouth Junction. By the time BR was formed in January 1948 they were all based at Salisbury and most of them remained there until withdrawn from service.
    • 30763-30772 were allocated to Stewarts Lane for working the Continental boat expresses. Some of these were later based at Dover marine.
    • 30773-30782 were allocated to Nine Elms. Almost all of these went to Dover Marine in early BR days but were subsequently more widely spread.
    • 30783-30793 were allocated to Bournemouth
  • 30794-30806 were to be found scattered between Ashford, Stewarts Lane, Bricklayers Arms and Higher Green on the formation of BR in 1948.

Accidents & Incidents

In the summer of 1946, locomotive 502 was hauling a freight train that overran signals and was derailed by trap points at  Wallers Ash, Hampshire.


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