He has a 3ph PME supply, he still working on his build so has a temporary supply box (DP switch, MCB, RCCD and pair of sockets)and earthed via Earth rod.
I recommended he installs a a 3ph switch fuse, taking the meter tails and then from that he can feed his garage 3Ph units as well as single ph domestic supply.
His Consumer units are about 8m cable run away from meter (and intended switch fuse location) ... he went to TLC and they provided his with a 3 core cable (non armoured) to create the switch fuse to Consumer unit link.
I was surprised that this cable has 3 core - brown, black & grey ......
Is it permissible to have grey as the earth conductor ? ........I have only used cables with bare earth wire and sleeved to green/yellow.
Is Grey the approved earth core for high current cables ?