British Rail Classes 253, 254 and 255

British Rail Class 253 and 254 High Speed Train
Class 253 set at Dawlish Warren in the 1970s
In service	1976 –
Manufacturer	British Rail Engineering Limited
Family name	High Speed Train
Constructed	1975 – 1982
Number built	58 trainsets (Class 253) 36 trainsets (Class 254)
Formation	2+7 cars (Class 253) 2+8 cars (Class 254)
Operator(s)	Western Region Eastern Region Scottish Region InterCity
Line(s) served	Great Western Main Line East Coast Main Line Cross Country Route Midland Main Line
Specifications
Car body construction	Steel
Maximum speed	125 mph (200 km/h)
Prime mover(s)	Paxman Valenta 12cyl 12RP200L
Power output	2,250 bhp (1,680 kW) per power car

Class 253, Class 254 and Class 255 are classifications that have in the past been applied to InterCity 125 high speed trains in Great Britain.

When built, from 1976, the InterCity 125 rolling stock was considered to be diesel-electric multiple units, with semi-fixed formations of power cars and intermediate passenger-carrying trailer cars. They were all numbered in the 4xxxx carriage series set aside for HST and Advanced Passenger Train vehicles. Numbers followed those allocated to the prototype Class 252 unit, so power cars were numbered from 43002 upwards. Class 253 were Western Region 2+7 (two power cars and seven coaches) sets operating out of London Paddington, Class 254 Eastern Region and Scottish Region 2+8 sets (with a second buffet car) operating out of London King's Cross.

However, because two power cars carried the same 'set number', problems arose when for servicing reasons different units were used on a train, which would then display a different number at each end. For this reason, British Rail abolished the initial numbering system and all individual power cars became identified as such, using the format 43 xxx - this number was previously carried in small digits in the bodysides, prefixed by a 'W', 'E' or 'Sc' to identify the region, thus the power cars were reclassified as Class 43 diesel locomotives and the trailer cars as hauled Mark 3 carriages, collectively known as an InterCity 125. Despite this change in designation, no power car or carriage was renumbered.

In 2002, Class 255 was allocated for the reformation of some HST power cars and trailers into semi-fixed formation trains, to be known as Virgin Challenger units, for use by Virgin Trains after the introduction of their new 'Voyager' trains (Classes 220 and 221). These formations would have had power cars sandwiching one Trailer First, a Trailer Buffet, two Trailer Seconds and a Trailer Guard Second, and were intended for use on Virgin CrossCountry's planned services between Blackpool, Manchester and Birmingham, and Paddington to Birmingham via Swindon. These plans came to naught as the Strategic Rail Authority planned to transfer most of the stock to Midland Mainline for their London-Manchester 'Rio' services.