An adverse possession claim allows one to claim possessory title by possessing the land and dispossessing the paper owner for consecutively 12 years of time. Time starts to run when the owner has been dispossessed of his land and the adverse possessor has taken possession of the land with the intention to exclusively possess the land. That is to say, the adverse possessor has, for example, fenced off or taken the key of the property and excluded the owner from using the land.
You should do a land search at the Land Registry to confirm the ownership particulars of the Lot of land. You should also keep records of the usage and take photos (with date/time stamp) of the land and your house (or other establishments) on that land to show that you have used the land for at least 12 years and that you have excluded others, including the paper owner, from using the land. Please also keep a record of utility bills, or communication with the paper owner and mark the timeline of the land usage.
If you and your family are under threat or harassment from the paper owner or its agents, such as verbal or physical abuse, or blocking the passageway to your home, please report to the police and document the details of the threat or harassment. If the situation is serious, you may have a right to apply to the court for an injunction to stop the harassment.
If you think you have a strong claim for adverse possession, you should not accept any offer from the paper owner of the land to pay rent until you have sought legal advice.