A team of engineers was assembled at the Railway Technical Centre in Derby in the early 1960s, to design and develop an Advanced Passenger Train (APT) capable of at least 125 miles per hour (201 km/h) incorporating many features not previously seen on British railways—such as tilting to allow higher speeds on curves.

[2] The APT project suffered repeated delays and in 1970, the British Railways Board (BRB) decided it would not be sufficiently developed to enter public service until well into the next decade, so a stopgap solution would be needed to reduce journey times in order to compete effectively with other modes of transport.

At the instigation of Terry Miller, Chief Engineer (Traction & Rolling Stock), the BRB authorised the development of a high-speed diesel train using tried and tested conventional technology for short-term use, until the APT was able to take over.

The design incorporated a driving desk around the centrally seated driver, a sound-proofed door between the cab and the engine room, and, unusually, no side windows.

[9] The fixed-formation concept was proven in trial running between 1973 and 1976, and British Rail went on to build 95 sets of production HSTs to transform InterCity services.

The production versions were mechanically very similar to the prototype, but differed considerably in appearance: the streamlined wedge-shaped front end lacked conventional buffers, and the drawgear was hidden under a cowling.

Lighter axle loading allowed the trains to travel faster than conventional services along lines not suited to full-speed running, such as Edinburgh to Aberdeen.

[17] By the start of the summer timetable in May 1977, the full complement of 27 Class 253 sets (253001–253027) was in service on the Western Region, replacing locomotive-hauled trains on the Bristol and South Wales routes.

[4] In 1979, HST services began in South West England, to destinations such as Exeter, Plymouth and Penzance, and in 1981 they were introduced to the Cross Country Route via Birmingham New Street.

More Mark 3 trailer cars were built in the 1980s for the Western Region Class 253s, making them eight-car rakes in common with East Coast and Midland Main Line services.

[22] A second world record for the fastest diesel-powered train, a speed of 148 mph (238 km/h), was set by an HST on 1 November 1987,[23][24][25][26] between Darlington and York with a test run for a new type of bogie for use on Mark 4 coaches on the same route.

On 27 September 1985, a special press run for the launch of a new Tees-Tyne Pullman service from Newcastle to London King's Cross, formed of a shortened 2+5 set, briefly touched 144 mph (232 km/h) north of York.

British Rail Class 47 locomotives still operated cross-country services from Cornwall and South Wales to the North-East via the Cross Country Route, and London to the Midlands/Welsh Marches.

Great Western Trains was formed out of the privatisation of British Rail and operated the InterCity routes from London Paddington to the west of England.

Great Western Railway retained 24 powercars and 48 coaches to form 11 four-coach sets for use on local services between Cardiff and Penzance, replacing the British Rail Class 158.[when?]

In January 2007 the first of GNER's 13 refurbished HSTs was unveiled with coaches rebuilt to the same 'Mallard' standard as its InterCity 225 electric sets with similar seating, lighting, carpets and buffet cars.

[citation needed] In 2007 the franchise was taken over by National Express East Coast (NXEC), which continued the re-engining programme begun by GNER, and completed the refurbishment of the fleet in March 2009.

[citation needed] Following an announcement by National Express that it would not provide further financial support to NXEC, the franchise ceased on 13 November 2009, and the operation of the route returned to public ownership.

In 2006, Grand Central obtained six Class 43 power cars to operate its London-Sunderland passenger service via the East Coast Main Line.

While at the works being re-engined, Grand Central added the orange stripe that appears on their Class 180 units, re-painted the front ends (this making them look more like the non-buffered HSTs), and re-numbered the power cars into the four-hundreds.

[citation needed] The Midland Main Line received a series of speed improvements over the next two decades, until it became possible for HSTs to run at up to 110 mph (177 km/h) on some sections.

After privatisation, the Cross Country Route was operated by Virgin CrossCountry, who replaced their InterCity 125 trains in the period 2002–2004 with Bombardier Voyager high-speed DMUs.

In a temporary operation dubbed Project Rio,[50] a large percentage of the stored Virgin CrossCountry power cars were overhauled and returned to service in an enlarged Midland Mainline fleet.

At Ladbroke Grove and Ufton Nervet, the accidents were ultimately caused by factors not involving the HST sets or their drivers, although the set involved in the Ladbroke Grove crash had a faulty AWS system;[86][87] however, the Southall accident was due to the HST colliding with a goods train which was entering Southall Goods Yard, crossing the main lines.

In addition, the leading power car of the set had a faulty Automatic Warning System which if operational would have alerted the driver to his error and possibly prevented the accident.

[101] More recently, HSTs have been replaced (or augmented) by high-speed Diesel multiple units (DMUs), such as the Bombardier Voyagers and the UK express version of the Alstom Coradia.

The problem was first raised in 2003, after Railtrack staff at Nottingham abandoned local clean-up and then track maintenance procedures due to an excessive buildup of sewage waste in the area.

[112] HSTs remained in operation after 2017, but sliding-door conversions of CrossCountry's fleet and the shortened sets for GWR and ScotRail have all included the fitting of controlled emission toilets.

[113][114] In 2019, HSTs were not permitted to operate passenger services on the National Rail network in their original form because various deficiencies made them non-compliant with accessibility regulations – in particular, the need to open doors manually.

The suspension was modified to operate on less stable track, and the cooling system and air filters adapted for the hotter, dustier Australian conditions.