I have found the aircon demon - the person who turns the office aircon down so low each day that I bring a jacket to work even when it's boiling out there.
And it's all made sense now.
Our aircon demon is a biker. He turns up in leathers and helmet having spent a bracing commute freezing his butt off, rain or shine. No wonder the sheltered indoors feels a little stifling to him!
This morning I caught him with his finger on the "on" button. Caught at last!