Law of the land: A former friend is interfering with the sale of my farm — can I do anything to stop him?

A reader said that someone he used to work with is removing the for sale sign from his property.

Dear Stephen,
I own a farm, which I am in the process of selling as I wish to retire and move abroad to sunnier climates. 

I never married and have no children or family relatives that helped on the farm. A neighbour helped me out on the farm for a number of years. He had a background as an agricultural contractor; he was out of work, and I needed some help, so he worked with me and I kept him on for a number of years.