If you dig a hole and bury a electrode tape, disc, etc then backfill with expensive concrete, but it doesn't give a good test result you have spent over £300 of the customers money without achieving the required outcome.
With a rod you just screw another extension on and drive it all down deeper.
Years ago two electricians installed a forty five feet long rod on the old power station site at Stourport on Severn, which is the bottom of Hartlebury Common a sandy heath using no more than a lump hammer.
