I am surprised someone (media) has not mentioned a possible terroristic act. I did see that LHR closed during the incident. I have not been watching the news cycle so forgive me if i am not up to speed.
An empty aircraft sitting on the remote, most likely after being cleaned and the crew rest area catches on fire?
Of course I am doing nothing but speculating at this point. Can anyone confirm that area of the aircraft is the crew rest area?