In 1987 and 1988, Regional Railways took delivery of 35 two-coach Class 155 units, built by Leyland Bus at its Workington factory, to replace older DMUs.

[11] The seven further Class 155 units that had been delivered to the West Yorkshire Passenger Transport Executive (WYPTE) in 1989 were not included in this plan.

[2][15] This new cab is notably smaller than the original one at the A-end, as the positions of the exterior doors were not changed during the conversion, and it was necessary to reduce the size of the vestibule slightly in order to provide enough space for the driver.

[11] Gangway connections are provided at either end to allow passengers and staff to walk between units working in multiple, in-class as well as 150/2, 155, 156, 158 and 159.

In October 2018 all eight passed with the franchise to Transport for Wales (KeolisAmey Wales), who acquired a further five from Great Western Railway in April 2019, five from Abellio Greater Anglia in December 2019, four from East Midlands Railway in January 2020 and another two from EMR in November 2020, which brought the total number up to 24 until a further two units were acquired.

[19][20] As at February 2020, Transport for Wales was the only train operating company to have modified 153s to comply with the requirements of the Persons with Reduced Mobility Technical Specification for Interoperability (PRM-TSI),[a] which came into effect on 1 January 2020.

[28] The trains have also been refurbished inside providing free Wi-Fi, plug and USB sockets, and maps of the West Highland Line on the tables.

[11] Class 153s were often found working services from; In the lead up to privatisation of British Rail, ownership of the fleet passed to Angel Trains (30) and Porterbrook (40) in April 1994.

[32] Upon privatisation, they were initially operated by Anglia Railways, Central Trains, First North Western, Northern Spirit, and Wales & West.

In December 2007, First Great Western received an additional Class 153 from Arriva Trains Wales, bringing its total to 12.

For summer 2011, two London Midland Class 153s were allocated to the South West for strengthening purposes, based at Exeter TMD for the duration.

Nine of those 14 units later left the fleet, with the remaining five moving to Transport for Wales in April 2019 after being displaced by internal cascading.

During 2012, Porterbrook began refurbishing the body and interiors and repainting them in base white with red doors and Greater Anglia logos.

In 2014, a rolling refurbishment of Abellio Greater Anglia's Class 153s commenced, which included new interior panels, tables, carpets and lighting.

This was due to take place in December 2008, but the delivery of the new units was delayed, and after several months of bustitution London Midland reintroduced diesel services from 15 March pending the completion of Class 139 testing.

The Class 139 received passenger certification from Network Rail in March 2009[35] and the service finally began three months later.

At one point in April 2020, only three EMR Class 153s were in service, following the implementation of an emergency timetable due to the COVID-19 pandemic, with all others being stored out of use as surplus to requirement.

[citation needed] All of the East Midlands Trains Class 153 units were repainted into the company's local lines livery.

It inherited the fleets previously operated by Arriva Trains Northern (ATN) and First North Western (FNW), whose routes the new franchise incorporated.

[42] The stripped out bodyshell of unit 153374 has been donated to the Llanelli and Mynydd Mawr Railway, for static use as a community cafe, at Cynheidre.

[45] In 2024 Go-op Co-operative Ltd. received approval from the ORR to run services between Swindon, Taunton and Weston-super-Mare under an open-access agreement using refurbished Class 153 units.