the earth cable is coming from the same direction as the 25mm phase and neutral meter tails. It was originally connected to the earthing bar of the consumer unit and is bare copper. I would say it must be 25mm. There are no bonding terminals on the CU.
I put the main earth cable in the earthing bar of the consumer unit. There should have been a 16mm cable run from this to the main earthing terminal and then all the services should have been bonded to this but that hasn't been the case.
I've just replaced a consumer unit from a rather ancient cartridge fuse and have noticed that there is no MET. Any ideas on how the bonding should be carried out in the absence of this?