^OP you are asking if you're being U.
Yes you are.
Farmer and lawyer here.
You would be trespassing on private land.
Land owners owe a duty of care even to trespassers. Next thing we know is that you've fallen in the ditch and broken your leg, can't work for 6 months and sue me for damages for not alerting you with a big sign about the ditch.
This is why you would be chased off the land and the landowner be perfectly reasonably peed off that you felt at liberty to camp without permission.
Ps. I'm dropping by your garden for a camp out, don't know when, I would have access right^
^^ This^^^
I am also a farmer (although not a lawyer). I have the good fortune to own a considerable amount of land , much of which is very pretty (think lakes, a river, ancient woodlands.. really chocolate box stuff).
Happily I am also quite remote so I don't have huge problems with trespassers but I do move a half dozen load on each summer. What gets me is the sense of entitlement - you would go fucking NUTS if I pitched up with 3 kids and a dog, lit a campfire and camped in your back garden.
Here's a radical idea , why not find out whose field it is and ASK PERMISSION FIRST? That way you're not trespassing but may also be able to relax , light a fire if the farmer allows you and enjoy your trip without the fear in the back of your mind that a pissed off farmer with some vicious dogs is about to appear over the hill and chase you off.
I have one family who camp by my lakes for a few days every summer, they first approached us over 10 years ago when my father ran the farm and he said okay then, now I'm in charge I don't see the need to change anything.
They just knocked on the door after someone pointed them in our direction, they were very polite and were at pains to explain that they wild camped a lot, never left any rubbish or human waste etc so father said okay then. They even offered to pay (which he refused).
Over the years trust has built up and they are more than welcome any time they like, we have had some good times with them fishing and barbequing together sometimes.
One year when the weather turned on them, we brought them up to the house for the night, gave them beds and dried out their gear for them. It saved them having to cut their holiday short and having to drive home with sodden kit and pneumonia.
The alternative had they just pitched up without asking would have been to chase them off into the distance that first time and would have done us all out of some good times... all for the sake of a bit of common decency!
If you're not sure where to find out who owns a piece of land and a farmhouse is not obvious then the local pub is a good place to start. The locals in my village pub could tell you who owns every blade of grass for several miles in every direction.