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1125 - Class 205 DEMU Hampshire Unit ‘Thumper’

Status Operational


The Hampshire Units were one of several classes of Diesel Electric Multiple Unit (DEMU) built by the Southern Region of British Railways. The Hampshire Units were designated as Class 205 under the Total Operations Processing System (TOPS). The Hampshire Units were built in three batches (although technically the last batch were Berkshire Units with smaller destination blind windows and a larger Guards van). The units were based on the 2HAP Electric Multiple Unit (EMU) that were being built at the same time. The DEMU’s were built at Eastleigh although the frames were constructed at Ashford. They were powered by a 500hp English Electric 4SRKT (4 cylinder, Supercharged, Re-engineered, Type K, for Traction) fitted with a Napier MS100 Turbocharger.

As originally built the units were not fitted with any silencer on the exhaust system although silencers were quickly fitted to pacify people who lived in the vicinity of railway lines that the units worked over!

The engines were uprated from 500hp to 600hp by replacing the turbo charger with a Napier MS200 and making modifications to the fuel system. The units had a design life of 15 years as it was envisaged that the lines over which they operated would have either been electrified or closed by the time that the units planned life cycle had been exhausted. In actual fact the units completed 47 years main line service with several examples passing into the hands of Heritage Railways and are now over 50 years old – a real tribute to British engineering.

1101 – 1118 were built in 1957 as two car units but were later fitted with a centre trailer coach to take the units up to three coaches.

1119 – 1122 were also built as two car units in 1958 which were later augmented to three coaches.

1123 – 1126 were built in the latter part of 1959 as three car units.

1127 – 1133 (Berkshire Units) were built as three car units in 1962.

The DEMU’s came to the Mid Hants line in November 1957, taking over from M7 steam locomotives. The DEMU’s reduced the journey time and saw an hourly service introduced on the line – even on Sunday’s. The units were so successful in arresting declining passenger numbers that overcrowding became a problem. In an attempt to overcome this problem the units started to be augmented by the addition of a centre trailer coach.

The original power bogies on the units had suburban gearing. During 1959 these bogies started to be removed for use in the new 4EPB EMU’s. The DEMU’s received new power bogies which carried express gearing. On the Mid Hants line units fitted with express geared bogies, especially the three coach units, started to struggle on the steeply graded line. In the train heat and leaf fall season the situation became quite desperate. In fact when the order was received to remove the centre trailer coaches on Mid Hants services one unit, already at Alton, shunted its centre coach to the sidings immediately! Some units were re-geared back to suburban ratios but still difficulties remained on Mid Hants services. Two units 1121 & 1122 had their centre trailer coaches removed and were dedicated for Mid Hants Services. However, three coach units were regularly seen on the line when the dedicated units were stopped for maintenance or repair.

UNIT 1125 (formerly 205025)

Unit 1125 was ordered as a three car unit and entered service between December 1959 & February 1960. The first recorded working of 1125 on the Mid Hants Line was on 21st April 1960 when it worked 1453 Southampton Terminus to Alton and 1553 Alton to Portsmouth services. Following re-gearing in October 1960 1125 was regularly seen on the line. 1125 suffered an engine room fire whilst at Alton on 30th August 1971 and was recovered back to Eastleigh by a Class 33 locomotive.

1125 was on duty on the Mid Hants line on 4th February 1973, the last day of BR services. On this occasion it was coupled to unit 1121 to make up a five coach train. 1125 left the Mid Hants line on the last day whilst working the 2002 Alton to Southampton service, it would not return again until May 2004. In June 1986 the unit was renumbered in line with the TOPS computer system and became 205025.

In April 1998 205025 was reduced to a two coach unit with the removal of its center coach. In September 1998 205025 was sent to Eastleigh for an overhaul where it received the engine that it uses in preservation. The unit was also painted in Connex yellow and white livery.

In 2003 new Class 170 diesel units started to appear on the Oxted – Uckfield line which started the final decline of the DEMU’s.

205025 was withdrawn at Selhurst depot in February 2004 when it became due for a bogie overhaul. The unit was sold to the Mid Hants Railway in May 2004 and was delivered to Alton by rail and under its own power on 18 May 2004.


Built at
Build year
Last major overhaul
Total built of class
34 sets
February 2004


3 car from new, 2 car set in preservation
Power output
600 hp
Prime mover
English Eletric 4SR KT fitted with a Napier MS200 Turbocharger