The London and North Western Railway (LNWR) Class B was a class of 0-8-0 steam locomotives. A development of the three-cylinder compound Class A (though this letter classification was not introduced until 1911), they had a 4-cylinder compound arrangement. 170 were built between 1901-1904.
Between 1904 and 1908, Webb's successor George Whale added leading pony truck to 26 engines, making them 2-8-0s and taking them into Class E (again from 1911). Between 1906 and 1908, Whale also rebuilt 10 with larger Experiment-type boiler to Class F, again adding a leading pony truck. (Two more Class Bs were also converted to Class Es via Class Fs). Neither of these conversions were particularly successful and as a result, 17 were rebuilt to Class D with 2-cylinder simple expansion between 1910 and 1917.
Whale's Successor Charles Bowen Cooke rebuilt a further 91 direct from Class Bs to 2-cylinder simple superheated LNWR Class G1 (also known as "Super Ds").
A boiler explosion destroyed No. 134 on 11 November 1921 at Buxton, leaving 10 in the class. All of these were inherited by the LMS in 1923, who allocated them the numbers 8900/16/19/23/28/37/8/46-9 but only applied half of these (8900/16/19/37/8) before withdrawal in 1927-1928. None was preserved.