Not strictly speaking on my own because there were a few other people with me, Security and computer engineers, none of which are much use in the real World!
I was called out to work one New Years Day for a power cut at work, not normally a major problem, stand by generators would start automatically and stop when the power came back on. There were a few odd things that would require a re-set and back home was the normal procedure.
This time the power came back on but the generator did not stop, so I rang the people who serviced it for us and was advised to hit the emergency stop. To be honest I can't remember the full sequence of events, but it stopped and then started again, so I hit the emergency stop again. This time the generator stopped and the emergency button fell apart! We now had a strange situation where the computers were running but the air cons in the data rooms were not.
Now we had a back up procedure as I am a mechanical engineer not electrical, so I rang the stand by electrician. He had gone away for the weekend, so I rang the manager; he was at Old Trafford watching Manchester United!
Temperatures in the data rooms were reaching critical and some of the servers were falling over by this time and the computer men were jumping up and down like Yosemite Sam!
I eventually managed to get hold of a contractor friend of mine and he found out the problem was caused by a voltage optimiser that had recently been installed incorrectly. I don't know the full story but it was something to do with the control circuit relay being set to different value to the normal power. All it needed was a potentiometer being turned down a notch.
As I mentioned at the start, strictly speaking, I was not alone but it certainly felt like it!
I found out later that we had caused all sorts of havoc at Heathrow Airport.