"I don't know...paint?"
Well, I went to investigate the mysterious black stuff....
At some point in the night the electrics had decided to overheat and catch fire. There used to be a security light near the roof. The whole thing has burnt and fallen without our night security guard noticing. I wonder what he was doing - couldn't possibly have been sleeping on the job, surely!
The bulb, despite falling to the floor, is still in tact. It could have been due to fluctuations in power supply, faulty fixings or a faulty wiring job. Those of you that have seen some of the electrics here will be surprised these things don't happen more often.
We are very glad that the wooden beams didn't catch light and nothing major was damaged. If it had been a light round the corner of the building they are attached to the wood. Then the whole roof could have gone up.