An RL FUUUU moment.
Just got to work, someone left me a note asking me to give the floor a clean, so I give it a sweep, degrease it and then start mopping it...when POP, and the lights go out.
There had been a leak earlier in the day and it tripped the light circuit, they reset it...and now, when I get into work it decides to trip and stay tripped...

Thankfully I have an arc lamp to provide some light and thank the gods that I still have mains electricity...for now...