if you were filiming them and/or had a security camera system, with output of this is was normally connected to the TV, and any terrestrial antenna clearly disconnected or not in use, then you would not need a TV license 😉
TV licensing is an odd organisation as it used to be part of the Post Office when they also did telecommunications, and is part government owned (BBC and Ofcom) and their officers have some investigatory powers but cannot enter anywhere without a warrant or do any heavy stuff without backup from the Police, same as with Ofcom.
Even if they can see the “telly” or any other device, if its clearly not regularly showing live programming of a UK terrestrial channel at the same time it is being broadcast nor can they prove it is being used for this purpose its difficult to prosecute you.
TBH even if GCHQ were to try to detect any signals from outside my house they would only pick up any combination of weather messages from German Coastguard, trance, progressive house and electro, telephone signalling tones, cats meowing and other animal noises as well as piratenhits, sea shanties and obscure documentaries in all of these languages, and I’ve met the local Ofcom chap anyway – who actually encouraged me to buy a new radio scanner as my old one was kaput but just said “if you hear any vessels in distress but the harbourmaster doesn’t seem to, then call the Coastguard” (you do get some upper class twits here whose nautical experience goes only as far as rowing club on the non tidal Thames and often use a handheld VHF or poor antenna and think it is just like a “mobile phone”, and I am not so far away from the sort of place where these fools are liable run aground…
