Ahhh, that's it

So we're sitting there last night feeling rather chilly. 'I don't understand it,' I said, 'upstairs it's as warm as toast. The boiler is obviously working.'
I sat down to think, cos I'm good at thinking, and started to feel all the radiators. They were all off but one felt ever so slightly colder than the rest.

This is where thinking comes into its own. 'I wonder,' I said to myself and tried the on off control. The radiator had been turned off. We never touch the heating controls and rely on thermostats to keep us warm. The only thing that I could think of is that some kindly soul turned the radiator off at Christmas and omitted to tell us. Thank you very bloody much.