Protecting commercial revenues.
This is more about protecting commercial revenues, setting a precedent for that (paid aerial drone photographs), than any real safety issue. I could maybe understand if something had happened (hit an overhead electicity cable etc) but nothing did. Complete waste of Police resources, and we as taxpayers are all paying for this pointless head clipping.
And yet, in other news, a girl aged 17 can't even walk back home a night in London without being sexually assaulted. So sad, that will blight her for life. The drone incident will be forgotten about tomorrow.