Phil, There is a location tab that stops it rotating and ensures correct alignment.
But never mind:
We Have A BoreholeI made up my more substantial slide hammer, and even using it like a maniac for quite some time had no effect. In places I could get a hacksaw blade into the gap the full two inches of cover thickness, but elsewhere it would not go in at all - managed to clear a bit of debris using it but nothing substantial.
So I decided to use the slide hammer as an attachment and do a tentative lift with the Fork Lift to put tension on the cover - no lid movement what so ever, and continuing the entire massive concrete structure started lifting

Clearing the turf away from round it, (to stop it falling into my nice water source!) I carried on lifting until a gap appeared showing
WATER - lots of water !
Getting my cable drawing fibreglass duct rod, I tried pushing it down - there was a definite circular 'thing' in the centre under water - presumably a pipe, and I was able to push at least 20 maybe 25 metres down the hole before feeling any resistance. All this was at an odd angle as the concrete structure was balancing on one key (my slide hammer) off the fork lift.
Common sense told me to lower it back before there were any accidents

So now I need to work out what's next
