There were no fire walls and no sprinkler system (not sure that would be a good thing with 275kV flying around)
There was redundancy to a certain extent but the fire took it out.
Heathrow had three main feeds, but two of the main terminals were mainly on one supply and switching over required power down and no one was sure if the other two could cope with a full load and they didn't want it to trip in the middle of the day.
why it caught fire in the first place? Don't know and haven't seen anything other than the TXs were pretty ancient.
