Ask H&H: can they take tractors in the field with my horses?

Q: I keep my two horses on a DIY livery yard and rent two stables and a field for my horses’ exclusive use. Because one of them is rather flighty, I requested that field maintenance is only carried out with my consent. I am happy to keep both horses stabled for this to be done.

Despite my request, the yard owner has taken a tractor into the field while my horses were grazing and maintains that he has every right to do so without prior warning. There has already been an incident on the yard where a tractor entered a field while horses were turned out, resulting in one of them galloping on to the road and being killed by a car. My own mare has previously panicked in the field and galloped into the fencing.