Introduced by Hunslet in 1943 these locomotives were based on designs from as far back as the 1920s. They were built to fulfil an order from the Ministry of Supply, some 300 machines being built in three years. Not all were built by Hunslet though, Robert Stephenson and Hawthorn, Bagnall, Barclay, Hudswell Clarke and Vulcan Foundry also being involved.

It was because of the association with the war effort that the class became known as 'Austerities'. The nickname 'Bediron' has also being applied because of the connections with wartime scrap metal drive during which metal bed frames, fences, pots and pans etc., were melted down to provide steel for industry.

After the war construction continued for industrial users, sixty were also sold by the MoS to the LNER who classified them J94. The last batch of 'Austerities' were built in 1964, the engines being fitted with mechanical stokers, rocking grates and special drafting arrangements.

Examples at Quainton