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Experiments with two double locomotives to France and Roumania during the late 1930's powered by Sulzer 'double-bank' engines had been successful, the four machines were still operating as Derby set to work on the BR/Sulzer Type 4's.
These early machines were too large for Britain's loading gauge, their LDA31's were pared down to LDA28's, more useful for fitting into locomotives destined for restricted European loading gauges.
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.
D1 was officially allocated to Camden (1B), but was quickly loaned to Derby (17A), a sequence of events that happened to the remainder of the class when they were delivered.
On the latter route they were active on the Manchester services alongside the D57xx Metro Vicks, in particular the 7.25 am Manchester Central - St Pancras, returning with the 2.25pm St Pancras - Manchester Central.
During the last quarter of 1960 most returned to Derby Works for attention to a variety of things.
The Type 4's continued to be occasional performers on the St Pancras - Manchester turns.
1958/59 The first of the frames for the BR/Sulzer Type 4's were laid down at Derby during 1958, they would keep company with Type 2's D5011-5013 in the early build out.
By the beginning of 1959 D1 - D4 were substantially complete in respect to bodywork, the fitting of the internal components followed, but seemed to occur at a slower pace than the Type 2's alongside.
Many manufacturers and engine builders had sent locomotives to almost all corners of the world, in some cases there was some twenty five years of operating experience to fall back on.