The Great Western Railway

Great Western Railway

The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...

 (GWR) 5700 Class is a class of 0-6-0

0-6-0

Under the Whyte notation for the classification of steam locomotives, 0-6-0 represents the wheel arrangement of no leading wheels, six powered and coupled driving wheels on three axles, and no trailing wheels...

 pannier tank steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

, built between 1929 and 1950. 863 were built, making them the second most-produced British class of steam locomotive.
The GWR had favoured Pannier Tank locomotives since 1911 when they had started rebuilding saddle tank  locomotives built between 1870 and 1905 into this style. By 1929 these older locomotives were in need of replacement.

The first 5700s were almost identical in appearance to several of the older converted locos (e.g.