Audit equals numbers equals stats.
So how do you quantify negative searches, or reassurance patrols, or deterrent.
How about a little bit of TRUST. We are a minuscule organisation compared to that of the NHS. My rather poor attempt at sarcasm was to highlight that it's an utter waste of time to try.
Once again, drones have their place, but do not wonder on to a forum espousing "knowledge" and not expect to be asked to show your working.