The Class 56 is a heavy freight-orientated diesel-electric locomotive. Upon its introduction, the type arguably represented the first of the "second generation" of British diesel locomotives. When specifying its requirements for the Class 56, BR stipulated that its bodyshell design would be based on Brush Traction's existing Class 47 design, minus some features such as the obsolete headcode panel. Accordingly, it features a stress-skin manner of construction that was paired with an all-welded monocoque superstructure assembly. Mechanically, the type shares considerable similarity with the Class 47 overall, including its double-cab design.