These were the last locomotives designed and built by the LMS and the unconventional design was influenced by the successful use of American S160 locomotives during the 2nd World War. Designed for ease of maintenance rather than aesthetics, they were constructed with a high mounted boiler and running plate for quick access to pipe work and auxiliary fittings with the result that they soon earned the nickname 'Mucky Ducky'. A total of 162 were built from 1947 to 1952 and worked across the LMR, ER and Scottish areas. the first 50 were built witha double chimney, which caused exhaust problems. The remainder of the batch were improved by fitting a single chimney and by 1952 the first fifty were all modified and fitted with the same chimney. With a cut down tender and enclosed cab the locomotives could be easily driven tender first making them suitable for routes with no turntables. They proved to be a very powerful and reliable locomotive well suited to mixed traffic work. BR started to withdraw these locomotives in 1963 but the last of these moguls survived until the end of steam in 1968. Sadly on No 43106 survived into preservation.