Heathrow Director - I think you might have taken what I was referring to slightly out of context as, ( aside from questioning the nature of my employment ), you've proceeded to raise the very concerns that I too have about this.
I.e. the fact that you ( with your radar ) might indeed know who is supposed to be ( or not ) in various bits of the London TMA and / or associated airspace, but that knowing such will not prevent somebody with intent from commandeering ( legally or else wise ) an aeronautical conveyance ( small or large ) then careering about overhead the Capital city and / or spearing themselves into the any building of their choosing.
Veritably, the law abiding people will indeed obey the law and some people might indeed find themselves prosecuted by it; but it’s the other buggers, the really dangerous ones, who we need to protecting from and this new edict (imho) does not offer much more in the way of significant protection from what we’ve had previously, i.e. a 9/11 could still, relatively easily, occur in London – regardless of airspace restrictions & edicts from Whitehall.