In 1933 the LMS ordered 40 more examples of the “Hughes Crab”, which had last been built in their works in Crewe. By this time, William Stanier had been chief engineer at LMS for two years. Since he brought experience from the GWR and still saw room for improvement for the locomotives, the locomotives were not built directly to the original design. As the greatest innovation, Stanier introduced the so-called “taper boiler”, a boiler that tapers towards the front. This not only saved weight, but also ensured better water circulation. The new boiler also had a pressure of 225psi compared to 180psi on the Horwich Mogul. Thanks to the higher boiler pressure, the diameter of the cylinders could be reduced, but at the same time the piston stroke was increased.
Preserved No. 42968 in 2009 at Kidderminster
Due to the changes, the locomotives were given a new designation, but like their predecessors, they were also assigned to power class 5 and were used for the same tasks as these. These locomotives also got the narrower standard tender of the Derby Works. From the 14th locomotive, a slightly modified boiler was installed. A total of 40 pieces were made in the short period between October 1933 and March 1934. No further examples were built, as Stanier immediately wanted to build power class 5 mixed-traffic locomotives with a 4-6-0 wheel arrangement, from which his famous “Black Five” arose. In contrast to the Crab, the first new Moguls were not phased out until 1963, but the last engines were also phased out in 1967. Only the penultimate locomotive built with the BR number 42968 has been preserved today. This was operational until 2013 and then came to a larger one Overhaul still ongoing in 2021.