As a matter of interest, obviously a footy match or a market is an 'organised gathering' but what about somewhere like Lakeside or Bluewater, where the crowds are bigger than 1000?
Does this mean I can with impunity cruise over Lakeside and its associated retail parks at 1500' agl but have to give our local team a wide berth if they are playing at home? (Not that they've ever attracted more than 1000 spectators.)