Trespass Act 1980, s 5
If someone is on your property, you can tell them to leave and to stay off your property.
If someone has trespassed on your property, or if you think it’s likely they will trespass, you can tell them to stay off.
You can deliver the warning verbally or in writing. If you give a written notice, it doesn’t need to say anything special, just that the person isn’t allowed on your property. But because lots of people don’t know that it’s that simple, you might want to use our sample trespass notice below. If you give any notice in writing, you should keep a copy to help show that you have given a warning, in case you need to go to the police later because the trespasser has come back.
You could copy the sample notice below or collect a form from your local police station which has a section you can fill in and return as proof that you served the notice, in case you need to complain again.