Lightweight

Even before the start of the Second World War, it was becoming obvious that the economics of Britain's railway system didn't add up: costs were high, staffing levels had been set in an era when labour was cheap, and both freight and passengers were haemorrhaging onto the roads.


Despite experiments stretching back to the late 1920s, it was only in the early 1950s that diesel multiple units were taken seriously, and the nationalised British Railways in 1954 launched the "Derby Lightweight" -- so-called because of the extensive use of light alloys in its construction.


A hundred units were built (more than 200 individual cars), most as two-car sets but with a handful of four-car units.


They were allocated to areas with extensive branchline systems, where a diesel multiple unit enabled on-train staffing to be reduced by 35%, and depot staffing by equally significant amounts (it is no coincidence that much of the publicity material around their launch emphasises their cleanliness, and they required much less maintenance than a steam engine).


East Anglia took a very significant number, and these units proved successful on both ex-Great Eastern and ex-Midland & Great Northern lines. As well as operating costs going down, passenger numbers very significantly increased.


Here a delightful Derby Lightweight speeds along the Yarmouth-Lowestoft line, its yellow "speed whiskers" setting off the Brunswick green livery.


The DMU experiment was judged a resounding success, and British Railways ordered vast quantities of new machines using the experience gained from the Derby Lightweights.


Ironically, the Derby Lightweights were retired early -- they were not compatible with the new fleets of DMUs and they had largely disappeared by the late-1960s.


That soaring cathedral-like window at the front was never repeated (and careful study of the photos shows that during their lives most of them had "strengthening bars" added). But the later DMUs repeated the design feature where passengers could look out at the tracks ahead -- sitting immediately behind the driver was especially prized.