"But they fill in there 'oles, so wassthe problem M8?"

For so many artefact hunters 'filling in your holes' is the hallmark of responsible detecting. So for them perhaps detecting on a site on Hardian's Wall is OK, the holes were filled in more-or-less tidily (and in the dark!)

Damage done by greedy artefact hunters at
Brunton Turret, passionately interested
in history (Photo copyright English Heritage)