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Short answer is no. The school is unusual in that a right of way thoroughfare runs through it. It is on a steep hillside with clearly defined boundary fences or walls only in some places. The disputed area has never been fenced off or used by the school .
The school can't claim it unless it is theirs.
The same applies you you, you can't claim it unless it is yours
Adverse possession rules have changed which means that you have to make an application to the Land Registry to register the land after 10 years possession
If you have not done this - then you do not own it
However if you can show that you have used the land for 20 years then you may have a prescriptive right of way
This means it can not be blocked off
This right becomes absolute after 40 yeasr
Therefore if you can show 20 years access, whilst you do not own the land, you certainly can not be excluded from it
Can I clarify anything for you about this today please?