Ktm250 - as briefly as I can put it, if you place a 50m dome over every property, vehicle or vessel, flying your UAV within that dome would, within the law, be illegal if you didn’t have control of that property, vehicle or vessel.
Regardless of that 50m dome it would be illegal to fly directly over the subject, i.e. you can fly round it but not directly over it.
Now 50m is quite some distance (about 162+ feet) and with the fixed fairly wide angle lenses used on consumer drones the object would appear relatively small in the frame. As a consequence some pilots get tempted to fly within that 50m bubble to get a better composition/image, post their work on social media and some troll, or even the CAA at times, will use that footage to bring trouble for the pilot.
If you do some research on YouTube you will find some contributors who graphically explain what the ANO says you can and cannot do - search for ‘Ikopta’ (real name Dylan) and look through his videos on the subject.
As I said previously some of the footage I’ve enjoyed on this forum do, technically, and to a small degree re this 50m rule, break the ANO - and being placed on the interweb COULD attract some unpleasant attention. I’m not into naming and shaming unless the footage was intentionally or recklessly unlawful, or clearly had placed persons at risk of injury. Remember quadcopters only have to lose a rotor, a motor to fail, or the battery to suddenly lose its charge and you have a bag of spuds dropping out of the sky at one hell of a speed.