As it happened for British Railways a number of options were taken and it was left for BR Derby to draw up some of the plans and construct certain of the locomotives equipped with the medium speed engines coupled to an electric transmission.
Derby had almost two decades of diesel experience, dealing with the familiar 0-6-0 shunters, the two LMS express passenger locomotives of 1947/48, the experimental Fell locomotive and the very beginnings of production of the BR/Sulzer Type 2's.
Also delivered at this time from a variety of builders were D224, 810, 2117, 3779, 5336, 6122, 8035 & E5010.
In many cases there was no definitive 'right' or 'wrong' answer, the global use of diesel locomotives was still very much on a learning curve, with some solid successes and also many dead ends.
Nevertheless these were still large engines particularly when coupled to the large generators required to convert that mechanical energy into electricity.
These heavy internal components required substantial framing and support from the body, which was also filled with auxiliary equipment, train heating boilers, water and fuel, all red flags for those trying to keep the axle loadings as low as possible.
Unable to keep the weight down to an acceptable level for the Civil Engineer both BR Derby and English Electric had to resort to the four-axle bogie for the big Type 4's, an option that the designers would have no doubt preferred to avoid.
Thus was born the early heavyweight diesel electrics, their bulk not being reduced by the Derby built Type 4's being named after mountains and certain English Electric Type 4's being named after large ships!