Hello. I am a solicitor with over 15 years experience. I will try to help you with this.
What reason does the farming neighbour give for claiming that the land is his and that he is entitled to £30,000? Your question discloses no basis for such an assertion? Do you have a solicitor acting for you in the sale? Have you discussed this with him?
£30,000 I think is an arbitrary figure. Not sure why exactly he feels he is entitled to the land, but as the owner is dead I think he's trying to get whatever he can, and I have a feeling he is being egged on by someone else. To get him off our backs I said we would offer £3,000 just to that it doesn't stop the sale of the property.
If you have a solicitor acting in the sale have you asked his advice. It seems you are the victims of a nasty little opportunistic scam.