There is no law of trespass in the UK. And landOWNERS are actually freehold owners who have the right to fence a piece of land and work that land. They do not own the land - they own what they put on the land. For proof of this, look at the hoops and licences that landowners go through to get extraction rights.
Ultimately the only land owner is the Crown. But if you enter the physical property that someone owns on a piece of land, without their permission, then you have committed an offence.
Very good book on the subject available through Amazon "Who Owns Britain ?".
There is an 18th century law which can be applied : if the landowner asks you 3 times to leave the land and you don't, they are able to call the police and ask for your removal. If you still failed to leave you would be arrested for any number of offences, but not trespass.
And there's nothing to stop the landowner/freehold owner pursuing you for damage to their property - crops, fences, animals etc - if they have the evidence that you caused such damage.
"An Englishman's home is his castle" is about as truthful as "the camera never lies" - of course entering his actual castle without his permission is an offence. But landing on one of his paddocks isn't.