Originally Posted by
LTN Phobia
It may be a good idea to have a flashing alarm there as well though, so that it is easier to notice. With the airport being full of sound and noise, it may get easily overlooked if it's just the subtle alarm sound, whereas an illuminated sign saying "Help required" with a flashing red light at the disable loo combined with the audible alarm may well draw people's attention much better.
There's an amber light above the door. I think it flashes (not that I've seen it in LHR but in hotels I've seen these flash).
The purpose of the light should be made clearer on the outside too, so if someone notices it then they realise not to ignore it.