 The exception were three from the 1936 batch, which used an experimental Metadyne system, and the final batch of six, built in 1985, which used controllers manufactured by Kiepe.Improvements since manufacture have included the replacement of low-level Ward couplers by buckeye couplers, which has resulted in less damage from shunting accidents, and the fitting of draught excluders and cab heaters for use in winter when the locomotives operate on sections of line above ground.A number of the machines were fitted with Automatic Train Operation (ATO) equipment to enable them to work on the newly opened Victoria line.