Probably / possibly related to your E. Line SNAFU -- one evening this week something fell on the wires at a station west of Paddington and hundreds of people were stranded on the trains for hours for 3-4 hours - If it hadn't been for all the passengers' smart phones with flashlights/torches it would have been total darkness. MANY people missed their flights out of LHR and they were eventually evacuated on to the tracks and led to safety.

Unfortunately that could happen on the Piccadilly line too (or any other electrified rail service.