Don't trust them to cut the correct side of a gate valve on a cylinder change. That was a bad bad day!
I've cut wrong side of an isolation valve, cold main, freezing cold water, upstairs cylinder cupboard.
Water everywhere, heart pumping rapidly, shaking like mad, trying to stop the flow with my hands, dust sheet, even taking my top off, whilst shouting down to my mate to turn the mains off, (I'm not very loud).
Finally mains turned off, recomposed myself, soaked up all water upstairs, with jumper, dust sheet, customers towel.
Went downstairs expecting to see a big bulge and water dripping from the ceiling, couldn't find anything. Turns out it all came out through one of them floor to ceiling built in cupboards that the customer doesn't use.
Customer didn't have a clue about what just happened, I didn't say anything.