The British Rail Mark 3 is a type of passenger carriage developed in response to growing competition from airlines and the car in the 1970s.

Production coaches entered service between 1975 and 1988, and multiple-unit designs based on the Mark 3 bodyshell continued to be built until the early 1990s.

Most of the surviving fleet of the Mark 3 and its derivatives were still in revenue service on the British railway network in 2020, however, as of 7 April 2021, 300 carriages have been sent for scrap.

[1] Under the chairmanship of Stanley Raymond, it was decided to reduce journey times further on long-distance trains by increasing line speed to 125 mph (200 km/h), where practical – the maximum considered possible on Britain's Victorian-age railways.

At the end of 1968, proposals were submitted to the Commercial and Operating Departments of British Rail for a new fleet of third-generation standard coaching stock, designed to run at 125 mph.

[citation needed] An important advance over its predecessor was the adoption of secondary air suspension between the body and the bogies, giving an exceptionally smooth ride.

Ancillaries, such as electrical and air-conditioning systems, were grouped together in discrete modules housed behind an aerodynamic skirting between the bogies; on the Mark 2, these were mounted above and below the passenger seating area.

The introduction by Virgin Trains of Class 390 Pendolinos in the early 2000s resulted in the withdrawal of the locomotive hauled Mark 3s.

Many have since been returned to service, both as locomotive hauled coaches with Arriva Trains Wales, Chiltern Railways as well as being converted for use with HSTs by Grand Central and CrossCountry.

[9] This required modifications to the coupling mechanisms and electrical systems to make them compatible with Class 43 power cars.

In July 2009, it was refurbished and repainted at Doncaster Works in the same style as the Pendolino and Voyager fleets, but with the British Rail seats and interior fittings retained.

Most Mark 3 carriages have no retention tanks, discharging onto the track via a U-bend/pipe near the bogies, and in the 2000s both the RMT trade union and politicians were concerned at the environmental impact of this legacy issue.

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 build-up of sewage waste in the area.

[16] In 2013, Transport Minister Susan Kramer branded the practice "utterly disgusting" and called on the industry to take action.

ATOC responded by stating that, as all new vehicles had to be fitted with compliant toilet tanks, withdrawal of the HSTs by the end of 2017 would solve the problem.

Sets delivered for Eastern and Scottish[citation needed] Regions (Class 254) contained eight coaches, originally in the formation TF-TF-TRUK-TS-TS-TRSB-TS-TS.

[citation needed] From May 1987 onwards, both HST and Mark 3 loco hauled sets were repainted and refurbished into the Intercity swallow livery.

These Mark 3 carriages have been extensively refurbished and modernised with the following enhancements:[20] The Driving Van Trailers have been modified with diesel generators to provide Electric Train Supply to the coaches when the locomotive is not running, such as when in terminus stations and when stabled.

[28][29] The service, originally charged for, eventually became free, although users either had to provide their own headphones (standard 3.5mm stereo mini-jack plug) or purchase a pair from the on-board Express Cafe for £1.50.

In addition to radio and video feeds, a GPS train-location screen allowed passengers to check and track train progress.

[30] Because of cost overruns partly caused by more stringent regulations in the wake of the Taunton sleeping car fire the order was cut back to 207.

In 1987, ten were leased to Danish State Railways[32] while in 1994, three were sold to Swiss bogie manufacturer Schweizerische Industrie Gesellschaft for tilt train testing.

The Republic of Ireland's national rail operator, Iarnród Éireann, ordered Mark 3 carriages built between 1980 and 1989, with bogies for the Irish gauge of 1600 mm (5 ft 3 in).

They were built with automatic plug doors, which initially caused some concern as additional time and resources were required to perfect them.

Most of the fleet was air-conditioned, except for a small number of coaches built as outer-suburban stock, which ran in push-pull configuration.

A number of coaches were first class, and there were several dining cars and five driving van trailers (DVTs) that included passenger seating.

In 2008, Iarnród Éireann began taking delivery of 22000 Class railcars, which led to withdrawal of all Mark 3 coaches.

A year later the carriages were transported from Ireland, and in the upcoming time redesigned as Belmond's new luxury train Britannic Explorer, which is scheduled to run from July 2025.