The British Rail Class 121 is a single-car double-ended diesel multiple unit. 16 driving motor vehicles were built from 1960, numbered 55020–55035. These were supplemented by ten single-ended trailer vehicles, numbered 56280–56289. They have a top speed of 70 mph, with slam-doors, and vacuum brakes. The driving motor vehicles were nicknamed "Bubble Cars" by some enthusiasts. The Class 121 is Britain's longest serving DMU, operating in passenger service for 57 years until 2017.
British Railways service
The Class 121 were built for use on the Western Region of British Rail. They were used on various lightly used branch lines, including the Looe branch line in Cornwall, the branch lines off the main line in the Thames Valley, the Bridport branch line, the Severn Beach line in Bristol and the Greenford Branch Line in West London. Unlike the earlier , which had a small destination indicator in the roof dome, Class 121 had a four-character headcode box in the roof dome, with the destination indicator inside the top of the centre cab window.
Current operations
Upon privatisation of Britain's railways, the Class 121 fleet was only operated by one passenger company, namely Silverlink, with several more units in departmental duties with Railtrack. Since Chiltern Railways retired its final two units in May 2017, there have been no examples left in revenue-making service. However, Network Rail operates one Class 121 for various departmental roles. This has been reclassified as a Class 960 departmental unit. Duties include route learning, video surveying of track and sandite application. In addition, the unit has been specially repainted in old BR blue livery. The unit is based at Aylesbury and was jointly used by Chiltern Railways for route learning.
Past operations
Silverlink
inherited a small fleet of four "Bubble Cars". They were mainly used on the Marston Vale Line from Bletchley to Bedford, as well as non-electrified lines in North London, such as the Gospel Oak to Barking Line. The units replaced the previous fleet of Class 108 and Class 115 units, and were supplemented with a fleet of Class 117 units cascaded from Thames Valley services. The four units, nos. 55023/27/29/31, were based at Bletchley depot, where staff repainted set L123 into its original British Railways green livery. The others remained in obsolete Network SouthEast livery. In 1996, set L123 was withdrawn from traffic, and the other three were hired to Great Eastern for use on the Sudbury branch to Sudbury. These returned to Bletchley in 1997/98. Two of the units were repainted into Silverlink's purple and green livery, and the third was repainted into Network SouthEast livery. The three units also received names from withdrawn Class 117 units.
The units were replaced on Silverlink duties in 2001 by Class 150 Sprinter units which had been cascaded from Central Trains. The units have all since been transferred to departmental duties.
In 2006, 121032 was purchased by Arriva Trains Wales for use on the Cardiff Bay Shuttle. The unit has been repainted into Arriva colours and was hauled to Wales in June 2006 to enter service in July. The unit finally entered service on 16 August 2006 but was withdrawn 3 days later due to a major problem with the engine. The unit re-entered service on the Cardiff Bay line on 14 September 2006. In March 2013, following further extensive periods out of traffic, 121032 was finally withdrawn from service, due to a terminal engine fault. It was subsequently transferred to sister company Chiltern Railways and moved to Aylesbury at the beginning of 2014 and was later sold into preservation at the Wensleydale Railway, moving north at the beginning of May 2015.
Chiltern Railways
In 2003, Chiltern Railways reintroduced "Heritage" diesel multiple units on its Aylesbury to Princes Risborough shuttle service. For this purpose, unit 121020 was purchased from Network Rail, and heavily refurbished to allow it to operate passenger services. It was repainted into Chiltern Railways blue livery. The introduction of this unit allowed the release of a Class 165 "Network Turbo" unit. This unit has been fitted with secondary door locking and other safety features, and thus was exempt from 30 November 2005 deadline for the withdrawal of all Mark 1 vehicles. Electronic destination indicators and internal passenger information systems were recovered from "Network Turbo" 165 032 at refurbishment and fitted to this unit. The external exhaust pipes were rerouted through the brake van area. In May 2011 a second "Bubble Car" was reintroduced to regular service. Unit 121034, previously based at Tyseley Loco Works, was refurbished for use by the Birmingham Railway Museum. It is painted in BR Green livery and was also used on Aylesbury to Princes Risborough services, when required. Both units were additionally used on shuttles, as required, between Aylesbury and Quainton Road stations, on the occasion of events at the Buckinghamshire Railway Centre. In March 2013, Chiltern Railways acquired 121032 from Arriva Trains Wales. It sold the unit for preservation in 2015. Chiltern's two final units were withdrawn from service on 19 May 2017, due to difficulties in obtaining spare parts, and will be sold.
Fleet details
Active units
Remarkably, considering the age of the fleet, the oldest unit was also the final unit withdrawn alongside 55034, which remained in daily service until 2017, whilst the youngest vehicle was the first to be dismantled. As of July 2014, 55021 and 55030 have also been scrapped.
Preservation
Class 121s have proved popular for preservation on heritage railways.
Order details
Model railways
In 2006 Hornby Railways launched its first version of the BR Class 121 in OO gauge. Since 2017 Hornby have produced a basic representation of the prototype as part of their Railroad range in BR Class 121 in BR Green.
