LNWR Class B

The London and North Western Railway (LNWR) Class B was a class of 0-8-0 steam locomotives introduced in 1901. 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 and 1904.

Rebuilds
Between 1904 and 1908, Webb's successor George Whale added a leading pony truck to 26 engines, making them 2-8-0s and taking them into Class E (again from 1911).
 * Class E

Between 1906 and 1908, Whale also rebuilt 10 with larger Experiment-type boiler to Class F, again adding a leading pony truck. (Two more of Class B were also converted to Class F via Class E).
 * Class F

Neither of the above conversions was particularly successful and, as a result, 32 were rebuilt to Class G with 2-cylinder simple expansion between 1910 and 1917.
 * Class G

Whale's Successor Charles Bowen Cooke rebuilt a further 91 direct from Class B to 2-cylinder simple superheated LNWR Class G1 (also known as "Super Ds"). The rebuilds from Class B to Class G1 continued under LMS ownership between 1923 and 1927.
 * Class G1

A total of 170 locomotives was built but No. 134 was destroyed in a boiler explosion at Buxton on 11 November 1921 leaving 169. The rebuilds (some under LMS ownership) totalled 159, leaving 10 unrebuilt.
 * Summary

LMS ownership
The London, Midland and Scottish Railway (LMS) inherited 53 unrebuilt Class B locomotives in 1923 and numbered them 8900–8952. The LMS continued to rebuild them to Class G1 and the number of unrebuilt locomotives dwindled to 10.

Withdrawal
The remaining 10 Class B locomotives were withdrawn in 1927–1928. None were preserved.