As with the provision of main-line diesel locomotives, where BR acquired classes with differing forms of transmission, so it was with the acquisition of diesel multiple-units, where, although the vast majority were fitted with mechanical transmission, a number were also supplied either with hydraulic transmission or as diesel-electrics. For the classes allocated exclusively to the Southern Region, four different classes of diesel-electric multiple-units were acquired between 1957 and 1964. Used predominantly on those lines over which the third-rail was yet to be installed, or on those routes which were deemed unlikely to be electrified and were under threat of closure, the units operated widely over the Southern Region area. Acquiring cult status amongst enthusiasts, a number have survived into preservation. This companion volume to the earlier three volumes will include a brief introduction allied to a variety of illustrations portraying the career of the units concerned.
