Post #207: "there are lights on the taxi line that take you around the corner. It may have been that the lights were off but it's not at all usual for them to be off at night time. I've taxied out there loads of times but I can't recall if taxiway M is light at night time. As far as I know M is only used by aircraft under tow."
Apparently, M has no lighting.
Have not found 4 cases of M being used by mistake
O3L threshold visible from B, before the left kink.
The building over 60 years old, before wide-bodies. Collision shear along line of windows - weak part of building.
The floodlights on hangars behind building would partially blind one to the presence of the low old building (floodlights visible in the passenger pics)