The Sulzer engined BRCW type 2 diesel electric locomotives were among the best designs supplied to BR under the modernisation plan. The well thought out internal layout and arrangement of air intakes proved superior to the BR Derby design, resulting in the redesign of the latter type and setting a template for the next generation of diesel power.
The Birmingham locomotives became favoured power for the highland line to the far north of Scotland, proving more reliable and comfortable than the similar BR Derby designed equivilents. The two designs, later BR class 26 (1160bhp engine) and 27 (1250bhp engine), were concentrated in Scotland, where the fitters' familiarity with the type ensured exceptional reliability, essential on the exposed highlands where a locomotive failure in bad winter weather could result in the train and passengers becoming stranded for days.