Just doing a periodic on some offices, and each office has a small mains unit fed with a piece of 16mm t&e, they are relying on the 6mm earth in the cable for the main earth. Now they are only a few sockets and lights in each office, no bonding needed or anything and if you do the aidiabatic equation the size is well in but I'm not 100% sure whether to code it on the report or not. There are individual isolators for each submain and these are fed with 25/16 earth tails so that covers the main earth cable size. This is the distibution area by the way, the real problem is the whole lot is fed from a single 100A supply, this wouldn't be too bad but there is a chip shop wired off it as well. Cut out too hot to touch pulling 75+ amps.