HEN the locomotive fleets used by the main freight operators were renewed after Privatisation in the late 1990s onwards, GM’s Class 66 diesel became a defacto standard, later supplemented by other types for specific operating requirements – including the 125mph Class 67s (introduced for postal services, then passenger and ‘Thunderbird’ duties), the higher-powered General Electric Class 70s, and Vossloh/Stadler’s mixed traffic diesel Class 68s and dual-mode
