The third digit represents the power classification, which was assigned (with a few exceptions) to all British Railways locomotives. The narrow gauge VoRR locomotives were not assigned a power class, but for TOPS purposes were allocated to power class 0. Three standard gauge locomotives have run on the mainline that were not previously in BR stock; "Lady Armaghdale" (Hunslet works No. 686 of 1898) was assigned power class 1F on the basis of its tractive effort, "Barbara" a Hunslet Austerity 0-6-0ST (works No. 2890 of 1943/rebuilt 1962 as 3882), assigned power class 4F on the basis of the classification given to LNER Class J94 of the same design, and the new-build A1 Pacific locomotive "Tornado" assigned power class 8P on the basis of the power class assigned to the LNER Peppercorn Class A1 on which it was based. Additionally, two engines in LMS stock but not BR stock were given their LMS power classification 1P.