By 1966 they began to be painted in corporate Rail Blue with yellow ends, the change generally coinciding with a works repair and the fitting of air brake equipment, the locomotives originally having only vacuum braking (the first so treated was D9002; the last to be painted blue was D9014). In the early 1970s they were fitted with Electric Train Heating (ETH) equipment to power Mark 2 air-conditioned coaches, while a couple of years later, with the introduction of BR's TOPS computer system, they were renumbered 55 001 to 55 022. In 1979, Finsbury Park restored the white cab window surrounds to their remaining six Deltics, making them distinctive, although these were later painted over when the locomotives were transferred to York during the rundown of the depot at Finsbury Park.