So they've recently found a memory stick in the gutter with all the current LHR secrets on it including emergency access points, evacuation plans, tunnels, and all in plain-text. Beggars belief but reminds me that in the 60s after all the evening birds had flown you could have walked a small army across the airport and nobody would have turned a hair.
I remember a bit of a scandal when some workers found that people were sleeping in some of the communication tunnels and all of a sudden properly lockable doors were fitted. I also remember that pumps operated 24/7 to keep the main access tunnels dry and I assume that that still carries on. Funny old place, not the same without Queen's Building or the old Terminal 2. Now I wonder if the additional runway is in jeopardy (again!).