Hence the issue with the aircon, when on a horrible cold wet summer evening when passengers board the train looking for a bit of additional heat on board, the driver isn't permitted to tweak the fixed point on the often chilly air con temperature.
Initially there was a 'Don't touch this without phoning Hitachi' policy. That has relaxed considerably over the last couple of years.
Lots of Train Managers have been shown how to change the saloon temperatures, and they are permitted to do so. The ones that haven't can always ring in and ask to be run through the procedure. The temperature is usually set to 21.5 degrees
IIRC▸ which is a much more sensible temperature than, for example, the Class 180s were set at, which
couldn't be changed by the crew - now that
was chilly!