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If a person does have a right of way, whether it be for vehicular or pedestrian access over a roadway or path, the mere erection of a gate on such a roadway or path is not deemed to infringe this right, provided the person is able to open the gate (ie it remains unlocked or the party is given a key for any lock attached to the gate).
Therefore, I am afraid that you are not legally entitled to prevent a gate being put up, provided you are able to open it.
I am sorry this is not the answer you were looking for, but it sets out the legal position.
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