The two prototype power cars emerged from the works in June and August 1972 and were initially numbered 41001 and 41002, but after a short period the entire set, including the passenger coaches, became reclassified as a diesel-electric multiple unit: British Rail Class 252.

The design was successful and led to production orders being placed for similar trains for the Western, Eastern, Scottish and London Midland regions.

The production power cars featured a redesigned front end without conventional buffers, although a rigid drawbar can be used to connect an HST to an ordinary locomotive.

Following the introduction of production HST sets, the prototype unit was withdrawn, the power cars passing to the Research Division at Derby.

In 1987, as electrification of the East Coast Main Line was under way, British Rail realised that the new Mark 4 carriages for the Class 89 and Class 91 locomotives were not going to be finished in time for the introduction of electric services on the East Coast Main Line so, in late 1987, a total of eight Eastern Region power car conversions were carried out at the Derby Engineering Development Unit, whilst the other six were converted by the diesel repair shop at Stratford to have the lower valancing removed and buffers fitted.

Later, Virgin Trains withdrew the HSTs when new Class 220 and 221 units were delivered, and nearly all of these power cars went into storage at Long Marston.

After years of storage, several of the power cars were bought by Midland Mainline to be part of Project Rio, special services running from London St Pancras to Manchester while major engineering works were undertaken on the West Coast Main Line.

These units were kept in the de-branded Virgin Trains livery throughout their time with Midland Mainline and put back in storage once Project Rio had finished in 2006.

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

[9] A qualifying requirement for the trial was that the engine should undergo a British Rail Type Test which was carried out between December 1993 and February 1994.

The successful results of the test cleared the way for installation of a VP185 in Power Car 43170 at Plymouth Laira Depot for in-service trials in the summer of 1994.

[10] During the late 1990s twenty-five HST power cars were re-engined with Paxman VP185 engines in order to improve fuel consumption and reduce emissions.

The increased speed and rapid acceleration and deceleration of the HST made it ideal for passenger use, and it slashed journey times around the country.

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.

During 1987, eight HST power cars were converted for use as driving van trailers (DVTs) with Class 91 locomotives during trials on the East Coast Main Line.

After the Mk 4 stock had been delivered, the HST power cars had the TDM equipment removed, and then reverted to their normal duties.

[18] Twenty-seven sets each with four or five carriages moved from Great Western Railway to Abellio ScotRail and were refurbished with controlled emission tanks and plug automatic doors.

[25] In 2021, RailAdventure acquired the six 43/4 power cars, plus an additional two for spares, for use on stock movements as part of its entrance into the UK market through the acquisition of Hanson and Hall Rail Services.

[34] On 2 May 2016 an open day was held at Bristol St Philip's Marsh depot with a line up of Class 43s from each operator (except CrossCountry) to celebrate the HST's fortieth anniversary.

At the event, power car 43002 (Numbered 253 001 as a Diesel Multiple Unit) was unveiled in original Intercity 125 livery, and named Sir Kenneth Grange after the Class 43's bodyshell designer.

[65] A report published in 2011 concluded that the Mark 3 coaches could remain in service as late as 2035, subject to some minor rewiring and enhancements required under disability legislation.

[67] Initially, high-speed Bombardier Voyager and Alstom Class 180 Adelante replaced numerous HST units, but all locomotives and sets were brought back into service as a result of increasing demand.

Some Great Western sets were cascaded to Abellio ScotRail to replace the Class 170 units, while others were retained by GWR to operate local services.

[69] Grand Central Railway leased five more Class 180 units cascaded from GWR to replace its HST trains and increase its overall fleet size.

[75] The Railway Heritage Designation Advisory Board nominated 43102 (43302) for preservation as holder of the record for being the fastest diesel locomotive on the planet.

[86] In addition to these twelve, Locomotive Services Limited have saved seven power cars, 43046, 43047, 43049, 43055, 43058, 43059 and 43083 along with three sets of Mark 3 coaches for use on excursion trains.