If we want to get into this, in Law in England and Wales then we start looking at Tort and civil liability. Unless criminal damage can be proved such as breaking fences or leaving litter, the civil law act of trespass is meaningless unless the land owner incurs a loss. There's a whole bunch of things they can get you for if you refuse to leave, but if you smile sweetly, apologise, pack up and walk away then no magistrate would touch this. In theory you can be pursued for damages, but these are based on the damage you do - which if you just walk on the grass is none.
Now clearly, as I have said before, if I know access is problematic then I will avoid exacerbating the issues. For example 20 years ago I avoided climbing at a North Wales crag when the landowner very publicly removed permission. I would not try access to contended hills such as Upper Park. BUT, if no one is actively complaining about access to a rural or mountain area then I'll use it. As Steve G1INK points out, without this attitude we wouldn't have the access we have now in the UK. The Scots have gone much further of course and formalising this attitude in their access law.
If we REALLY want to get into details then we can all pack up and go home, because even on a PROW or CROW Act Land we don't have the right to erect antenna systems and operate radios, without express permission. So you would need to seek permission every time someone operated. Of course we don't do this, we use common sense, which I suggest needs to be applied to general access!
Tread carefully, try not to cause offence, but don't get too hung up on common law (Tort) that is really there to stop individuals depriving others of their rights over land, or profiting from it when they shouldn't.