At the outbreak of the Second World War, the War Department had initially chosen the LMS 'Jinty' 3F 0-6-0T as its standard shunting locomotive, but was persuaded by Hunslet that a simplified version of their more modern 50550 design would be more suitable. The first was completed at their Leeds works at the start of 1943.
A total of 337 were built for the War Department by 1947 (on orders placed during the war), with two further engines having been built for collieries (without the permission of the Ministry of Supply). With the end of the war and then the reduced need for locomotives, the military started to review its fleet:
As the final War Department locomotives were being delivered, the National Coal Board was placing orders for identical locomotives to be used at collieries. Between 1948 and 1964, 77 new "Austerity" locomotives were built for the NCB.
Needing more locomotives for military depots, the Army ordered 14 locomotives in 1952 to supplement the original 90 they had retained.
The Yorkshire Engine Company also built 8 locomotives in 1954 for use in ironstone quarries and at Scunthorpe Steelworks. It is thought the design and many parts were sold to them by Hunslet as part of a subcontract for Yorkshire Engine Co built GWR 9400 Class 0-6-0PTs (ordered from Hunslet).
Hunslet undertook the rebuilding of many NCB locomotives and when the Army started to sell off locomotives again in 1959, they bought 15 examples that were to be rebuilt and sold on. The NCB bought 13 of these, the 14th was sold directly into preservation and the final locomotive was scrapped without being rebuilt.
The total number Austerity 0-6-0STs built to 485.
The Austerities continued in industrial use with the NCB into the 1970s with a small number surviving until the early 1980s. The examples that survived the longest were those fitted with mechanical stokers and Kylpor Blast pipes or Giesel ejectors to improve their performance and reduce smoke.
Not all have survived intact; the boiler of RSHN 7135 of 1944 was used on the replica Broad gauge locomotive "Iron Duke" built in 1985. At least one has been turned into a Thomas the Tank Engine look-a-like, and another into one of Donald and Douglas also from The Railway Series.
The Kent and East Sussex Railway has three preserved austerity tanks.
This class of engine forms the basis of Wilbert the Forest Engine and Sixteen the Steelworks Engine from the Railway Series of children's books by Christopher Awdry. Wilbert is named after the author's father the Rev. W. Awdry who created the series.