Thanks for your question.
A person seeking to claim land that they do not own must prove what is termed "adverse possession" to the land registry in order to have it registered in their own name. In order to do this you must have had possession of the land and used it as your own for either 10 years (if the land is registered) or 12 years (if the land is unregistered).
You will have to seach to see if the land is registered. You can do this by submitting LR form SIM marking the area with a plan. The LR will tell you if this is registered (I assume that it will be).
You would have to apply to the LR for adverse possession by submitting form ADV1 with a statutory declaration sworn in front of a solicitor describing your use of the land and the chronology. This can be accompanied with other documentary evidence which confirms what your statement says (ie. Photos, statements from others etc).
The owners would be at liberty to object to the application and you would have to litigate if they do.
The alternative is obviously to offer to purchase the land from them.
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