The British Rail Class 98 is a Total Operations Processing System (TOPS) classification that has been used to cover all steam locomotives used on the mainline in Britain, but also has a particular usage for the three Vale of Rheidol Railway-design 2-6-2T locomotives that remained in the ownership of British Rail (BR) after the end of mainline steam traction in August 1968.The Class 98 series has also been used for privately owned steam locomotives registered to run on the mainline since 1971.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.The fourth and fifth digits usually represent the locomotive's BR number, with a few exceptions.