Their lights were not working and the MCB was tripping with a loud bang and a flash when they tried to reset it..
I got the phone call this morning along with a load of verbal abuse as I worked on their lights last week so it was obviously my fault.
It took me 30 seconds after arriving to work out that someone had stolen their outside light and that there was a LE short on the cable sticking out of the wall. It took me another 30 seconds to charge them a £30 call out.
A nice polite phone call would have resulted in a £5 charge for my fuel.