Two British companies, Drone Defence and Eclipse Digital Solutions, adapted existing jamming technology to create the "Sky Fence." A network of roughly 20 "disruptors" is being installed in and around the prison's perimeter to create a 600-meter (nearly 2000-foot) high, virtual wall through which drones shall not pass. Well, that's the idea when Sky Fence goes into operation next month, anyway.

As Drone Defence CEO Richard Gill explains, the invisible wall was developed a preventative measure that isn't designed to knock airborne drones out of the sky. "It will look like it is bouncing off a forcefield. The operator's video screen will go black and they will lose control. Drones made in the last few years are all designed to return to the last point at which they were under control if the signal is lost. It won't bring the drone down because if it did and it hit someone or caused damage that would create issues of liability."