Does Heathrow bear a resposibility to prove anything to you or any other random person on the internet? You seem to be insinuating some conspiracy by asking vague questions.
The responsibility on the police is to confirm sightings before arresting people for flying drones over the airport (the police arrested a couple for flying drones over Gatwick when there was no evidence of drones over Gatwick).
The lawmakers should support their power grab with evidence but they are more interested in grabbing power.
There's really no disadvantage to airport authorities acting like this and only positives for them in protecting themselves from financial risk in the case that there is a drone. Plus, perhaps new powers will be passed that prevent them having to actually invest in anti-drone technology. Double-win!
Even if their contracts with airlines don’t lead to penalties then an airport that gains a reputation for drone shutdowns will lose passenger and airline business over time.