The British Rail Class 98 is a Total Operations Processing System (TOPS) classification that has normally 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 locomotives that remained in the ownership of British Rail (BR) after the end of mainline steam traction in August 1968. The locomotives on the Vale of Rheidol Railway were the only steam locomotives ever officially to carry the British Rail corporate blue and the double arrow logo.
The number 98010 was assigned to an locomotive acquired by BR in 1987. This locomotive also worked the Vale of Rheidol and was sold along with the steam locomotives. 98010 was built by the Brecon Mountain Railway, using parts supplied by Baguley-Drewry.
Vale of Rheidol locomotives
These three steam locomotives, numbered 7-9 by the Great Western Railway and British Railways, were the only ones to survive in BR's ownership after the end of mainline steam traction in August 1968. Under TOPS they were allocated Class 98 and were nominally numbered 98007-98009, but these numbers were never actually carried on the locomotives.
Registered steam locomotives
thumb|right|46115 Scots Guardsman - a class 7 engine, TOPS number 98715
The Class 98 series has also been used for privately owned steam locomotives registered to run on the mainline since 1971. The first two digits are the class designation, in this case 98, the remaining three digits are allocated as follows:
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