These dual-voltage trains are capable of operating on 25 kV 50 Hz from AC overhead wires or 750 V DC from a third rail.

Built in two batches in 1987–88 and 1990, the units were primarily used on the then-new Thameslink service from Bedford to Brighton and various other destinations south of London.

Some of the fleet was also used by Connex South Central and latterly Southern on various services operating out of London Victoria, including flagship expresses to Brighton.

The British Railways Board then developed plans for what would become Thameslink, and the newly created business sector of Network SouthEast inherited responsibility for the project in 1986.

[citation needed] They were also required to have emergency end doors in the cabs,[8] due to the twin single-bore layout of Smithfield tunnel preventing normal train evacuation.

The formation of the second batch of sets was similar to that of the earlier units, with the addition of first-class seating at one end of the train for use on longer-distance Bedford to Brighton services.

In 1997, seven of the Class 319/0 sets were converted especially for use on Connex South Central express services between London Victoria and Brighton.

They retained their low-density layout, but the lounge area was replaced by standard seating following their return to use on Thameslink services.

In the period 1997–99, Thameslink arranged for all of its 319/1 units to be converted at Eastleigh Works for use on the shorter-distance Luton to Sutton/Wimbledon services, then known as 'Thameslink CityMetro'.

First-class compartments were refurbished with new carpet, retrimmed seats and chrome-plated heater panels, apart from unit 319444, which retained its 1997-designed interior.

Unit 319425 was renamed Transforming Travel for the occasion and showcased the following improvements: The refresh took place at Railcare Wolverton works and also featured both a mechanical overhaul (under the solebar) and a full exterior relivery, again in vinyl.

Orion High Speed Logistics is aiming to launch its first trial service conveying parcels and light freight in April 2021, with the Midlands to Mossend now likely to be the debut flow.

Orion unveiled its first modified 319, No 319373, at Eastleigh in August 2020, and from 18 to 20 January 2021 showcased the unit to potential partners and customers at Maritime Transport's Birmingham Intermodal Freight Terminal at Birch Coppice.

[citation needed] A week after the start of the new franchise, West Midlands Trains leased additional Class 319 units, which had previously operated with Thameslink.

Twenty Class 319/3s transferred to Northern Rail for newly electrified lines in the North West, with the first units entering service in March 2015 after a light refurbishment.

In December 2016, it was announced that some 319 were to be converted to Class 769 Flex bi-mode multiple units by Brush Traction at Loughborough, and were planned to enter service with Arriva Rail North in 2018.

[20] In August 2019, it was confirmed that all 319s were planned to leave Arriva Rail North to be replaced by 17 of the 26 Class 323 units operated by West Midlands Trains.

In September 2023 it was reported that Northern Trains planned to withdraw its Class 319 fleet by the end of 2023,[22] later delayed until January 2024.

[23] When British Rail was privatised in the mid-1990s, the first 13 units (319001–013) were used for outer-suburban services by Connex South Central, with some temporarily losing their 25 kV AC overhead equipment.

It later went on to sublease Class 319/0 units to First Capital Connect for use on the Thameslink route, before eventually releasing the entire fleet.

The modifications, which were carried out by Brush, will enable units to operate on electrified and non-electrified routes, using both 25 kV AC overhead wires and 750 V DC third rail.

[45] In February 2020, a further three were ordered to allow services to be introduced the Midlands to Scotland via the West Coast Main Line.