I had wired up a central heating system all complete but the gas had not been installed. Told the customer that when the gas engineer turned up all he had to do was switch on the isolator and it was good to go.
Two days get a call from the gas fitter, boiler won't fire up. Have you switched on the main isolator? Yes, have you switched on the isolator next to the boiler? Yes. Have you turned up the room stat, cylinder stat? Yes.
B*gg*r! I drive back twenty miles to find two plumbers and the gas fitter all looking forlornly at the boiler . "I have to be somewhere else" says the gas fitter, "I was told it was ready..blah,blah,blah"
I took a look at the boiler and said,"perhaps you want to turn the f******** boiler stat up then"
The look on three faces was worth the drive back.