....and you would be perfectly happy to rely on that system not being interfered with by some nation-state that has a bone to pick with Downing Street right at the moment?
Some miscreant tossing a bucket of foil confetti out the window could probably mess with things a bit as well I expect! Poke a microwave out the window (with door interlocks disabled) and turn it on? (doubt it'd have the range but hey, one can imagine... :) )
Release some large foil-based helium or hydrogen balloons? Bring back barrage balloons!