Although all built at
Crewe Works, they were designed at
Horwich Works and were developed from the Horwich Mogul, the
LMS Hughes Crab 2-6-0. They had the addition of several features brought over from the
Great Western Railway by newly arrived
Chief Mechanical Engineer William Stanier, most notably the
taper boiler (Stanier would have been familiar with the
GWR 4300 Class). In an effort to please Stanier, Horwich had designed a GWR style top-feed cover and showed him locomotive 13245 with this fitted. However, Stanier disapproved and had it replaced with the normal LMS cover. Due to a higher boiler pressure than the
Crabs the cylinder diameter was smaller and could thus be mounted horizontally, the only Stanier design to do so. Like the
Crabs they were connected to a Fowler tender that was narrower than the locomotive. When built the first ten locomotives had no water pick-up gear fitted. They were initially numbered 13245–13284 (following on from the
Crabs), but as standard locomotives, in the
LMS 1933 renumbering scheme they were renumbered 2945–2984 in 1934 (the
Crabs becoming 2700–2944). BR added 40000 to their numbers so they became 42945–42984. They were always painted black, and this was lined out except during the austere periods of the 1940s and towards the end of steam. From the end of 1934 Stanier turned to a larger
4-6-0 for his mixed traffic class, this being the
LMS Black Five Class. ==Details==