I had a sparks and his lad turn up on a job I was on to help out , as the job they went to had blown out , this was back in the 80s , it was remedialls following a periodic , I said to hem you might as well get on with the grommets and sleeving the earth wires on the sockets , I was working on the lighting , I turned my back for one minute and they were only going to do it with sockets still live , I stopped them right away and the sparks said Oh its all right its only the earth wires were touching ,, I couldn't believe it , I had to explain to them that the earth wire has to be considered as a live part also if the circuit is live and that the sockets should be isolated before they start work ,,,and to think he had a lad with him as well ,,,, the lad I had with me couldn't believe it also .