Due to a lack of expertise, this often involved the pairing of traditional locomotive manufacturers with various firms within the electrical sector, even though the latter typically had very limited experience of the railways.

[2] In accordance with these policies, BR ramped up its efforts to convert its fleet, placing numerous orders within a short timeframe for diesel locomotives to several different specifications with various manufacturers.

[3] The design also shared some similarities with the contemporary British Rail Class 15; both locomotives adopted the road-switcher layout that had been rapidly becoming the standard approach on the railways of both North America and Australia at the time; they were also both powered by an 800 hp (600 kW) Paxman 16YHXL prime mover.

[3] According to Bradley, North British found it difficult to translate their steam engineering skills to the newer diesel and electric traction designs.

However, there was considerable complications encountered during the type's construction, which has been typically viewed as not unexpected in light of a general lack of experience with mainline diesel traction on Britain's railways, and as such did not come as a surprise to many officials at the time.

There, the type underwent evaluation against the rival designs, but were promptly relocated to nearby Stratford depot on the Eastern Region, where they remained for the rest of their operating lives.

[3] Being both non-standard and fairly unreliable, the locomotives were an obvious candidate for early withdrawal despite barely being ten years old as BR planners were coming to this conclusion.