Steam Locomotives of British Railways - Classification

Classification

After initially using letter prefixes (E for ex-LNER, M for ex-LMS, S for ex-SR, and W for ex-GWR locomotives, as used for other inherited rolling stock), a numbering scheme was decided on in March 1948. Generally ex-GWR locomotives retained their numbers (and hence were able to retain their cast brass number plates), and it was decided to add 30000 to the Southern numbers, 40000 to the LMS numbers and 60000 to the LNER numbers. There were some exceptions though.

BR adopted a slightly modified version of the LMS classification system, itself based on the Midland Railway's system. Each locomotive class was given a number 0–9 that signified its power, 0 for the least powerful and 9 for the most, with a suffix of F or P, indicating freight and passenger roles respectively. Freight power ranged from 0–9, passenger from 0–8. Many locomotives were used for both roles, in which case they were given two class numbers, the P-rating first e.g. 3P4F or 6P5F. A slight change from the LMS system saw those where the freight classification (x) equalled the passenger classification (also x) reclassified as xMT, MT standing for mixed traffic, e.g. for the LMS Black Five locomotives, LMS 5P5F became BR 5MT. Mixed traffic locos had power in the range of classes 2–6.