The origins of the Class 153 date back to  1990, when British Rail needed replacements for its ageing fleet of  Class 121 and 122 'Bubble Car' diesel railcars for use on the quiet  Cornish, Welsh, North-Western, Norfolk and Lincolnshire branch lines, as well as augmenting rural two car units.
Originally built  as a two-car Class 155 'Super Sprinter' by British Leyland between 1987  and 1988, using a construction technique similar to that used in the  Pacers, pre-formed panels were riveted together, creating a lightweight  body on a welded floor assembly. Introduction was rapid, but teething  troubles with the door mechanisms soon emerged, consequently the fleet  was taken out of use and modified, with the Class 156 units taking over  the duties. The conversion to Class 153 was carried out by  Hunslet-Barclay at Kilmarnock between 1991 and 1992, with 70 vehicles  being produced. The layout of the original non-cab ends was different  from the original cab end, so the ends are noticeably distinct with the  vehicles not being symmetrical.
Powered by a 285hp Cummins  NT855-R5 Diesel, working through a Voith Hydraulic transmission, the  maximum speed of a Class 153 is 75 mph, making it perfectly suited for  small cross-country services. They are fitted with standard BSI  auto-couplers, allowing them to work in tandem with other multiple units from the 14X and 15X Classes fitted with the same coupler, as well as  newer units like the Class 170. In 2019/2020, five former GWR 153s moved from Northern to Abellio ScotRail for use on the West Highland Line  attached to Class 156s as 'active travel' carriages. These units have  had their interiors heavily modified to carry up to 20 bicycles, along  with large bags and sports equipment.