These locomotives were originally built in 1965 – 66 for the West Coast Route electrification, and have undergone many modifications since, in this case making them a specialist heavy haul freight locomotive. They normally operate in pairs hauling freightliner trains between Felixstowe, Willesden, Crewe and Scotland. Originally 100 locomotives were built, learning lessons from various earlier designs. Electrical control is by camshaft to DC motors, with individual motor packages capable of isolation. These re-geared examples have also had their electrical train heating supply isolated. The class is much reduced from the original 100 examples originally built.