Very big gun !
For those of you who think this is all a bit of a joke I can assure you that the RAF are taking this all very seriously.
Any light aircraft who enters the zone without clearance can expect to be met by a Puma, you can expect the crewman at the door to show you a large board with instructions.
If you fail to comply with these instructions you are likely to find yourself on the business end of a very big gun. One round from this is likely to stop you Lycoming leaving you to find a large open space to land on.
I would recomend Wormwood Scrubs, it will be convenient for the prison!