 The Class 312/0 units moved to the Great Eastern Main Line following the arrival of a more modern Class 317 fleet.The 312/1 subfleet consequently moved to the London, Tilbury and Southend Railway, displacing older Class 302 and 305 units.The section of 6.25 kV on the GEML had been converted to the now standard 25 kV, meaning the exclusive dual-voltage capability of this subfleet would continue to be useful, the line still being dual-voltage at the time.