The LNER B1 4-6-0s were introduced in 1942, the first being No. 8301, which was named SPRINGBOK as it coincided with a visit to the UK by South African President Jan Smuts. The first 40 of the class were named after breeds of antelopes and other animals becoming known as 'Bongos' after No 8306 BONGO. Before 1948 a total of 274 were built by the LNER with a further 136 following after nationalisation in 1948. The prototype was built at Darlington and was the first 2-cylinder main-line locomotive constructed for the LNER. With cost saving a wartime priority the LNER's draughtsmen went to great lengths to re-use existing patterns and to economise on materials and labour. Extensive use was made of welding instead of steel castings. Thompson, the designer of the class, ordered many of them to be constructed by two outside builders: 290 came from the North British Locomotive Company of Glasgow and the Vulcan Foundry contributed 50. No. 61057 was destroyed in an accident in 1950, but the first normal withdrawal was No. 61085 in November 1961. The remaining locomotives were withdrawn between 1962 and 1967.