Minion said:The ideal option would be a concrete base, or concrete rings with locked manhole or gate and a key issued to each key holding club.
I suspect Cadw will want no less than a full restoration to original status, or as close as possible, given that the ground has been irreversibly disturbed. Anything less would give the perpetrators, and others, an excuse to do the same sort of thing again if they think they can "get away with it". There are procedures in place for gaining consent. Ignore them, as was done, at your peril.