The (redundant) thermostat in the lounge. This is a remnant of the old heating system that optimistically assumed one thermostat in a multi-roomed barn would provide a meaningful control system. It's still there because it's prettier then a hole in the wall.
The current system works on deeply complicated algorithms based on size of building, the temperature outside, the phase of the moon and whether it's a Tuesday. It calculates what temperature the radiators need to be to ensure a perfect temperature for everyone, and heats the radiators to a seemingly random temperature instead. I can hear it humming the tune to 'Share and Enjoy...'
Anyway, we had a couple of energy surveyors round today with a view to providing a grant towards possible energy-saving measures; so when the question is next asked 'What did the EU do for us?' we'll put you in the cold and draughty room...