The earth riveted on seems a good idea though, so when you drill through the capping as if it wasn't there, even if you happen to be using a recharageable drill, it'll short to earth and take the breaker/fuse out, without you might not short anything, and possibly end up with a undetected broken ring, or you fit a rawlplug in and screw a screw in while holding the metal shaft of the screwdriver... (ok then, a small slither of the damaged cable pokes through one of the gaps in the rawlplug)