The message
from Andy Wade contains these words:

Some further time later I found that there was also an earth wire link
back to the company fuse block but I have never got round to
disconnecting the earth road although from time to time I wonder whether
it is doing any good at all. Should I disconnect the earth rod?

You may as well leave it alone. It won't do any harm and it might do a
tiny little bit of good.

It can stay then at least until I decide to put some insulation and
screed on top of the existing floor. Even then it could stay but it
would look a bit odd with the insulated earth wire disappearing into the
concrete. I don't suppose for a moment I would be able to pull it up by
4" so the clamp stays above the surface.

--
Roger Chapman