A couple of years ago I sat on an aircraft at Manchester for two hours waiting for it to be de-iced before the hop down to Heathrow; I was going to London for a meeting so had only a notebook with me.
Had the flight left on time I would have got to my meeting easily. Two hours later there was no point in making the trip. I explained the situation to cabin crew, who checked with the Captain, and they happily let me get off and go home!