Are you referring to what is commonly known as "Squatters Rights"? The evidence necessary to claim "adverse possession" of property depends on whether the property is registered with the Land Registry or whether it remains unregistered. It is now very difficult to claim adverse possession of a registered title as notice of your claim is now given to the registered owner. The registered owner can of course object to your claim. With an unregistered title the owner cannot always be traced and therefore as long as you can show at least 12 years possession of a property then your claim may succeed. (I think the term is 12 years). Have you lived at the property, used keys to a locked door etc? The Land Registry would grant you a "possessory title" to the property. You can read more on the Land Registry's website in their Practice Guides.