The ‘4-CIG’ was the first of a new generation of express multiple units which were based on the ‘4-CEP’ units built for the Kent Coast electrification. A major difference was the decision to house the traction and control equipment previously carried on the driving vehicles, in an intermediate Motor Brake Second. The front-end appearance was tidied-up with rounded edges to the driving ends and the jumper cables enclosed in a recess, and Pullman type gangways. 36 ‘4-CIG’ sets and 19 of the corresponding ‘4-BIG’ buffet car sets were ordered from York in 1962 to replace the pre-war Pullman and pantry car sets on the Central section. Another 102 ‘4-CIG’ and 9 ‘4-BIG’ sets were subsequently introduced for the Waterloo-Portsmouth services and, more generally, to replace Southern Railway design stock on both the South Western and Central divisions. The units were originally finished in the standard plain green livery with small yellow warning panels as shown by No. 7313 on a Waterloo-Portsmouth Harbour service.