British Rail Class 74

The BR Class 74 was a small class of ten Bo-Bo electro-diesel locomotives rebuilt between 1967 and 1969 from withdrawn Class 71 Bo-Bo electric locomotives, intended as a more powerful development of the Class 73 electro-diesel concept for the Southern Region's demanding boat train and Pullman services from London Victoria. The Class 71 had been the Southern Region's original AC overhead electric locomotives built for the Kent Coast electrification in the 1950s, and when made redundant by the extension of third-rail DC electrification, their bodies and mechanical components were reused as the basis for the Class 74 rebuilds at Vulcan Foundry.

The Class 74 used the same 750 V DC third-rail supply as the Class 73 for electric operation, but was fitted with a more powerful Paxman Ventura 6YJXL diesel engine producing 650 hp for diesel-mode working — a modest improvement over the Class 73's 600 hp, but in a heavier and more complex locomotive that proved less reliable in service than the purpose-built Class 73. The ten locomotives were numbered 74001–74010 and entered service in 1968–69.

The Class 74's service life was disappointingly short. The Paxman diesel proved troublesome in the complex dual-mode electrical environment, and availability was poor. By 1977, less than ten years after the last examples entered service, the entire class had been withdrawn. None was preserved, and the Class 74 stands as one of the less successful Southern Region traction experiments of the period — a rebuild programme that produced less reliable results than either the original Class 71 or the simpler Class 73 it was meant to develop.