It might be added that the Reds are somewhat anal about their precious sanitised airspace in a way that seems rather OTT. Firstly, the area is, as said above, utterly vast and nothing, but NOTHING is allowed to fly in it once it is activated.
Thus if the local plod helo or air ambulance deploys to the display "to be seen" it will not under any circumstances be allowed to launch during the display. Not even on pre-planned low level exit routes that do not affect the Reds' line of flight. The entrance of a Police helo on task into the area will stop the display unless things have changed since I was in that business.
No one else seems to need this huge amount of airspace although many other display aircraft use a larger amount of sky to display than the reds.
It smacks just a little of a Prima Donna attitude, though I'm sure no one has ever accused the Reds of anything like that in the past...