Hello and thanks for using Just Answer.
I am Al and am happy to assist you with your enquiry.
I am afraid that unless you have a right of way in the Deeds to the field, which it oes not sound as if you do, then the neighbouring property can stop you from using this privat elane to gain access to your field.
Under law, where a person does not have a written right of way, a right of way is created PROVIDED they have exercised and used it for at least 20 years, without hindrance or dispute. I note you have been using the lane for only 10 years, so unfortunately you have not acquired any legal right to carry on using it if the owner is now asking you to stop.
I am sorry this i snot the answer you were looking for, but it sets out the legal position.