The British Rail Class 207 (3D) diesel-electric multiple units were built by BR at Eastleigh in 1962. The fleet had a lifespan of 42 years. The Southern Region class 201 to 207 DEMUs are nicknamed 'Thumpers' due to the noise their engine units make.

When new the class were used on the Oxted Line, and were mostly concentrated on services between London Victoria and Uckfield and Eridge to Tonbridge via Tunbridge Wells. Other routes that the units operated included occasional workings on the Marshlink Line, the Three Bridges to Tunbridge Wells Central Line and the Cuckoo Line. Following the closure of the last two of these routes the unit gained workings on the Redhill to Tonbridge Line, and were known to deputise for 3R units on the North Downs Line to Reading. Most units were withdrawn in 1987 following the electrification of the Oxted Line's East Grinstead branch. Four of the seven surviving units were used on the Reading to Basingstoke Line between 1988 and 1993; once this had finished three were withdrawn and the fourth sent to join the other three survivors on the Marshlink Line; between 1995 and 1998 this included through services from Ashford International to Brighton. After this the class operated on the Marshlink Line between Ashford and Hastings and the Oxted Line between London Victoria and Uckfield for privatised companies Connex South Central and Southern. The final three units were withdrawn in August 2004