looked at a job the other day (db change) there was no earth from the incoming supply no visable earth rod,only an earth block supplying the db with a 2.5 going to somewhere under the floor boards i suspect to the mains water/gas(boxed away somewhere will find later). the owner ( inherited house) rang e-on who said your sparky can put the earth in.i always thought we weren't supposed to mess with "their side". just wondered on others opinions would you earth from the neutral incomer or add earth rod