Was initially planned as early emblem, has been produced with late crest
Thompsons first, and most successful locomotive design, the B1 4-6-0, was a simple, rugged, all-purpose machine, whose relatively low axle weight gave it a route availability wider than most Gresley engines of comparative power. the first engine, No. 8301 'Springbok', was completed on December 13th 1943. 6 days prior to entering traffic.
Thompson's dislike of his erstwhile superiors long-established three cylinder practice, worked to his advantage under wartime austerity. Through their unsophisticated two-cylinder system of propulsion, and use of available materials with lower erecting expenses, the B1, that supplanted the V4, was precisely the right type of locomotive for the conditions prevailing during and after the war. Under BR ownership, production was perpetuated since the 4-6-0's coincided with the stipulated policy of simplicity in building abd service. Externally, more square-rigged than the preceeding Gresley products, the B1 was provided with modified B17 class boilers and cylinders. Allied to these were Thompson's individual pattern of bogie and LNER standered tenders.
No fewer than 410 engines filled the class at termination of construction in 1952, in favour of BR standard equivalents. The North British Locomotive Company completed a major proportion of the total for both LNER and BR. The first forty B1's were named after species of antelope - hence the occasionally quoted 'Antelope' class. the succeeding 18 were named after directors of the LNER - but the majority never bore individual identities.
The B1's were dispersed throughout the LNER network, and subsequent relevant BR regions, displacing a considerable range of elderly pre-1923 machines.