Stanier Class 4P 2-6-4 Tank Locomotive
LMS Class 4P no 2500, National Railway Museum, York (3-cylinder variant)
Thomas's Pics, CC BY 2.0, via Wikimedia Commons (exposure and composition modified)
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LMS Class 4P no 42575, Nantwich Railway Station (2-Cylinder Variant)
Ben Brooksbank / Up Bank Holiday Special at Nantwich Station(Wikimedia Commons CC BY-SA 2.0/Recomposed)
Technical Data
Introduced: 1934
No. Built: 243 (37 3-cylinder, 206 2-cylinder)
Wheel arrangement: 2-6-4T
Having made some slight modifications to the Fowler 2-6-4T design, Stanier then produced his own design of the locomotive, primarily intended for use on the London to Southend line. The first variant, produced in 1934, had a tapered boiler, and three cylinders as opposed to the Fowler-design's two; the third cylinder being added in order as an attempt improve locomotive performance. Although intended for the Southend line, the design did see service on other parts of the LMS network.
However, tests showed that the 3-cylinder arrangement was not producing any significant performance gains over the Fowler 2-cylinder locomotives, and the design underwent further modifications, mainly to produce a 2-cylinder version. The initial batch of eight locomotives had domeless taper boilers; separate dome and top feeds were added to later batches of the class. This variant could be found all over the LMS network.
The locomotives were generally considered to be a good design, with the last example being withdrawn in 1967.
| Locomotive Numbers | Year Built | Works | Cylinders |
| 2425-2475 | 1936 | Derby | 2 |
| 2476-2494 | 1937 | Derby | 2 |
| 2500-2536 | 1934 | Derby | 3 |
2537-2544 | 1935 | Derby | 2 |
2545-2609 | 1936 | North British | 2 |
2610-2617 | 1937 | North British | 2 |
2618-2651 | 1934 | Derby | 2 |
| 2652 | 1939 | Derby | 2 |
2653 | 1940 | Derby | 2 |
2654-2662 | 1941 | Derby | 2 |
2663-2670 | 1942 | Derby | 2 |
2671-2672 | 1943 | Derby | 2 |
Preservation
One example of the 3-cylinder variant survives (no. 2500, as seen above) as an exhibit at York Railway Museum. It has never steamed in preservation. No examples of the 2-cylinder variant have survived.