British Rail Class 123
A mixed four car DMU stands at Manchester Piccadilly in 1984. The two driving coaches are from a class 123 and the middle coaches are from class 124 units.
In service	1963–1984
Manufacturer	Swindon Works
Family name	First generation
Replaced	Steam locomotives and carriages
Scrapped	1984–1987
Number built	40 (Ten 4-car units)
Number scrapped	All
Formation	DMBSL-TCK-TSL[RB]-DMSK
Capacity	24 First class, 176 Second class seats (units with buffet 32 second class less)
Operators	British Rail
Depots	BG Hull Botanic Gardens[1] LA Laira
Lines served	Western Region Eastern Region
Specifications
Car body construction	Steel
Car length	64 ft 11+1⁄4 in (19.793 m)
Width	9 ft 3 in (2.82 m)
Height	12 ft 9+1⁄2 in (3.899 m)
Maximum speed	70 mph (113 km/h)
Weight	146.75 long tons (149.10 t; 164.36 short tons)
Prime mover(s)	230 hp (172 kW), 2 per power car
Power output	920 hp (686 kW)
Bogies	B4
Multiple working	Blue Square
Track gauge	4 ft 8+1⁄2 in (1,435 mm)

The British Rail Class 123 was a design of diesel multiple unit built for British Rail in 1963. They were the last first-generation DMUs built for British Railways and were built at Swindon Works. Ten of the four-car sets were built and introduced in 1963. The units bear a visible similarity to the British Rail Class 309; however, there is no 'relation' here as the two types were built by different manufacturers for different markets.

Details

Swindon-built DMUs, including the Class 123 and 124, had a structure and internal construction with much more in common with BR coaching stock (British Rail Mark 1) than they do with many DMU classes. The carriage underframes were longer (Mk1 standard main-line 63 ft 5 in (19.33 m) frames versus the 57 ft 0 in (17.37 m) frames common to most 1st generation DMUs) and the units were provided with mark 1-style 'Pullman' gangways instead of the 'British Standard Gangways' fitted to most contemporary DMUs of the period. It was also unusual for a first-generation DMU to sport a front-end gangway. None of these units survive today.

Operational history

They were originally intended for use on services from the South Coast to Wales, but only briefly used on services from Portsmouth to Cardiff and Bristol. When introduced they were concentrated on services between Swansea, Cardiff, Birmingham, Derby and Crewe and between Cardiff and Bristol. While still in their original green livery the units were trialled on services between Plymouth and Penzance on the Cornish Main Line as an alternative to loco-hauled services.^[2]

They were displaced in 1970 to outer suburban services from London Paddington to Oxford and Newbury, without the buffet cars.

All were stored in April 1977 but reprieved later that year for services from Hull to Doncaster, Sheffield, Manchester and occasionally to Leeds. All were withdrawn in 1984 and stored at Hull Botanic Gardens TMD.

Nine 2-car sets composed of a class 123 DMBSL and class 124 DMC were formed at Hull in 1984 in case introduction of the class 141 'Pacer' units was delayed, but they were never used in service.

Further use

One of the buffet cars, 59831, was rebuilt as a Class 309 AC EMU griddle car and renumbered 69108. It replaced a griddle car that had developed an underframe fault. Buffet car 59828 was converted to departmental dormitory coach in 1970 and used on the rail profiler train, then converted to a stores coach and used until 1987.

After withdrawal, the Leyland Albion engines were removed and used as spares for the class 115 DMU.