Delivered in two batches, a prototype build of six locomotives followed by a production run of a further 43 locomotives, on renumbering to TOPS the Class 73s as these were classified were renumbered into two Sub Classes. 73/0 in the number range 73001 to 73006 for the prototype batch then 73/1 in the number range 73101 to 73142 for the production variant. E6027 was an early casualty and no allowance was made for this when renumbering of the fleet was implemented.

73001 to 73006
73101 to 73142

The 73/2 Sub Class was created for those Class 73 dedicated to the London Victoria to Gatwick express service and initially twelve members from the 731XX series were renumbered into the 732XX series between 73201 and 73212. This round of renumbering was carried out in reverse order in that of the twelve selected to be ‘GatEx’ 73s 73102 the lowest numbered 73/1 became 73212 whilst 73142 the then highest numbered Class 73 became 73201. There were two later additions to the 73/2 Sub Class with 73112 being reclassified and renumbered to 73213 however the other addition was 73135 which was renumbered to 73235.