The DP2 design earned a reprieve in 1965, when the National Traction Plan of that year identified a need for an additional 50 Type 4 locomotives. By this time the Class 47 fleet were starting to suffer serious problems with engine stress cracking, a problem which necessitated the derating of the fleet to 2580hp. At the same time, DP2 and its 16CSVT engine had proved far more reliable than expected. Negotiations took place with English Electric for a production batch of 50 locomotives for use on the Eastern Region. English Electric intended to build the new batch as similar to DP2 as possible but the British Railways Board (successor to the BTC) had produced a standard locomotive cab with a flat front and headcode box and also had specific requirements relating to the engine room and other equipment. English Electric produced several alternative front-end designs including one with a wrap-around windscreen but the standard front-end design was eventually adopted for the class.